Thin film forming apparatus using laser

ABSTRACT

A thin film forming apparatus using laser includes a chamber (1), a target (5) placed therein, a laser light source (10) for emitting laser beam to target (5), and a substrate holder (3). When target (5) is irradiated with laser beam (16), a plume (15) is generated, and materials included in plume (15) are deposited on the surface of a substrate (2) held by substrate holder (3). The laser beam emitted from laser light source (10) has its cross section shaped to a desired shape when passed through a shielding plate (4804), for example, so that the surface of the target (5) is irradiated with the beam having uniform light intensity distribution. Therefore, a plume (15) having uniform density distribution of active particles is generated, and therefore a thin film of high quality can be formed over a wide area with uniform film quality, without damaging the substrate.

This application is a division of application Ser. No. 08/158,844 filedNov. 29, 1993, U.S. Pat. No. 5,622,567.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thin film forming apparatus usinglaser and, more specifically, to a film forming apparatus using laserused for forming thin film having functions and to form thin filmshaving large areas.

2. Description of the Background Art

FIG. 148 is a conventional thin film forming apparatus using laserdisclosed, for example in, Japanese Patent Laying-Open No. 4-45263 whichapparatus includes a chamber 1, a substrate 2, a substrate holder 3, aheater 4, a raw material target 5, a nozzle 6, an inlet window 7, acondenser lens 9, a laser unit 10, a turntable 11, an XY stage 12, acontrol apparatus 13, a motor 14, a plume 15 and an evacuating apparatus17.

The operation will be described. Laser beam 16 emitted from laser unit10 is condensed by condenser lens 9, passes through laser inlet window 7of chamber 1, and irradiate raw material target 5 placed on turntable 11in chamber 1. At this time, the turntable 11 can be rotated by means ofmotor 14. This is to make uniform laser irradiation by rotating rawmaterial target 5 so as to prevent local generation of craters caused bysputtering of the same portion of raw material target 5.

At the portion of target 5 which is irradiated with the laser beam,plasma is generated abruptly, and in the process of cooling of theplasma in several ten ns, there are generated isolated excited atoms andions. These groups of excited atoms and ions have the lives of at leastseveral microseconds, which are emitted in this space to form a plume 15which is like a candle flame. Meanwhile, a substrate 2 is placed fixedon a substrate holder 3 opposing to raw material target 5, and theexcited atoms and ions in the plume 15 reach substrate 2 and aredeposited thereon, forming a thin film.

In substrate holder 3, a heater 4 for heating the substrate is provided,so as to enable post annealing in which the film deposited at a lowtemperature is annealed at a temperature higher than the temperature forcrystallization to provide a thin film of superior quality, and allowingas-deposition in which the substrate itself is held at a temperaturehigher than the temperature for crystallization at the time ofdeposition so as to form crystallized thin film at the site. In theas-deposition method, sometimes an active oxygen atmosphere is used aswell. For example, as shown in the figure, a nozzle 6 for supplying gasincluding oxygen is provided so that the atmosphere around the substrate2 is made an oxygen atmosphere in forming a high temperaturesuperconductive thin film, whereby generation of oxide on substrate 2 ispromoted.

In view of enlargement of the area of thin film formation, substrateholder 3 is mounted on XY stage 12, so that the position of forming thethin film can be moved. First, a control signal corresponding to anoscillation pulse of laser unit 10 is transmitted to XY stage 12 throughcontrol apparatus 13. The XY stage 12 is driven based on the controlsignal, and moves the position of forming the thin film on the substrate2 at every laser pulse. Consequently, a uniform thin film can be formedon a wide area. In the conventional example, when XY stage 12 is notdriven, the area of thin film formation is limited to 10 mm×10 mm (withthe variation of film thickness distribution of ±10%), and when the XYstage is driven, the area can be expanded to 35 nm×35 nm.

However, in the semiconductor industry, formation of a uniform thin filmover a wafer of 6 to 8 inches in diameter has been desired, andconventional thin film forming apparatuses using laser could not meetsuch demand.

FIG. 149 shows another prior art example disclosed, for example, inJapanese Patent Laying-Open No. 4-114904. Referring to the figure, 18denotes an oxygen ion source, 19 denotes oxygen gas and 20 denotesoxygen ion beam. The process for forming a thin film in this example isthe same as that of the above described prior art example. In such athin film forming apparatus using laser, laser beam in the form of veryshort pulses of ten to about several ten ns is directed to the target,and the target material in the form of atoms, molecules or clusters aresupplied onto the substrate only at the time of irradiation, so as toform a thin film. The excimer laser having extremely short pulse widthand high energy has such advantage that (a) it allows generation of alarge amount of target raw material to be deposited on the substrate sothat the rate of thin film growth can be much increased, and that (b) athin film of which composition is not very much changed from that of theraw material target can be obtained. However, the excimer laser maydegrade the quality of the film due to insufficient crystallization. Inorder to promote crystallization of the raw material in the form ofatoms, molecules or clusters deposited on substrate 2, heating ofsubstrate 2 by a heater provided in substrate holder 3 so as to keep thesubstrate at a temperature higher than the temperature forcrystallization has been proposed. However, if the substrate is kept ata high temperature during thin film formation, it may induce degradationof the substrate or undesirable reaction, which is inconvenient for thefunctional thin film from electronic or mechanic point of view.Therefore, in this prior art example, in order to reduce problemsaccompanying heating of the substrate, oxygen gas 19 is introduced toion source 18 when raw material target 5 is irradiated with laser beam16 so that substrate 2 is irradiated with the generated oxygen ion beam20, whereby oxygen is supplied to the thin film and the temperature ofcrystal growth is lowered by the oxygen bombardment. Consequently, inthis known example, a Y₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thin filmcan be formed at the substrate temperature of 600° C.

However, the conventional thin film forming apparatus using laser hasthe following problems.

First, since the area of film formation which can be formed by one plumeis limited, it has been impossible to form uniform thin film over alarge area such as over a wafer having 6 to 8 inches in diameterrequired in the semiconductor industry.

In addition, there have been the problem of degradation of the substratederived from high temperature of film formation and lower quality of thethin film caused by undesirable side reaction induced. In addition, whenthe film quality is to be improved by using active ion seeds, there hasbeen possible damage of the substrate caused by ion beams, and thereforeit has been difficult to improve the quality of the film.

Further, film formation parameters such as intensity of condensed beamincident on the target, condition for laser oscillation, position of thetarget, pressure for film formation and so on have been set initiallyand thereafter these parameters are not controlled. Therefore, delicatecontrol of the film quality such as change in composition or orientationof the film which depends on composition of the surface of the target oron sudden change in energy of the particles incident on the substratecould not be done.

SUMMARY OF THE INVENTION

In order to solve the above described problems of the prior art, anobject of the present invention is to provide a thin film formingapparatus using laser which allows formation of a thin film having highquality and large area with uniform film quality distribution, withoutdamaging the substrate.

Another object of the present invention is to provide a thin formingapparatus using laser allowing delicate control of film quality, bycontrolling various conditions during the process for forming the thinfilm using laser.

The thin film forming apparatus using laser in accordance with thepresent invention includes, as basic components, a chamber havingevacuating means, a target placed in the chamber, laser beam irradiatingmeans for directing laser beams to the target, and substrate holdingmeans holding a substrate on which a substance included in a plumegenerated from the target by laser beam irradiation is deposited.

In accordance with the first aspect of the present invention, the thinfilm forming apparatus using laser includes means for shaping crosssectional shape of the laser beams emitted from laser beam irradiatingmeans.

Therefore, the laser beam can be changed to generate a plume suitablefor forming a thin film having a high quality over larger area with theenergy density distribution at the surface of the target irradiated withthe laser beam made uniform.

In accordance with the second aspect of the present invention, in thethin film forming apparatus using laser, the light intensitydistribution of the laser beam emitted from laser beam irradiating meansat the target has a prescribed linear extension.

Therefore, the light intensity per unit area when the beam is directedto the target can be increased, and the plume generated from variouspoints of light condensation can be overlapped with each other, so thatthe distribution of plume generation has flat portion over wider range.

The light intensity distribution preferably has angular, comb or curveextension.

In accordance with the third aspect of the present invention, the thinfilm forming apparatus using laser includes means for scanning thetarget with the laser beam emitted from laser beam irradiating means.

Therefore, the target can be irradiated with the laser beam uniformlyover a wide range, and as a result, uniform plume can be generated overlarger area.

Preferably, either means for changing direction of the laser beam byusing a rotatable polygon mirror, or means for changing the direction ofthe laser beam by using an acoustic optical element controlling thedirection of light by sound wave is included as the means for scanningwith the laser beam in the present invention.

Alternatively, laser beam deflection means may be used as means forscanning with the laser beam. Preferably, means for vibrating orrotating a mirror, an electro optical deflection element, an acousticoptical deflection element, or a deflection element of a transparentbody having a heater is included as the laser beam deflection means.

In accordance with a more preferred embodiment of the present invention,the target has a cylindrical shape, and the means for irradiating laserbeam includes means for irradiating inner circumferential side surfaceof the target continuously with the laser beam. The inner peripheralside surface of the target has, for example, a prescribed taper towardthe central axis. Further, it includes a reflection mirror having aninner circumferential side surface tapered in the reverse direction tothe inner peripheral side surface of the target, which faces, with anO-shaped light transmitting window formed in the chamber interposed, thetapered inner circumferential side surface of the target.

In accordance with the fourth aspect of the present invention, in thethin film forming apparatus using laser, the laser beams irradiatingmeans emits pulse laser beam, and it further includes means for movingposition of laser irradiation emitted from the laser beam irradiatingmeans on the target such that the position circulates in a prescribedperiod, and means for controlling relation between laser pulse frequencyand the speed of moving the position of laser irradiation on the targetsuch that the same position on the target may not be irradiated twice ormore by a plurality of pulses of the laser beam.

Therefore, the plume are not generated concentrated at a specificportion, and therefore a thin film can be deposited over a wide areawith uniform film thickness distribution.

In accordance with the fifth aspect of the present invention, in thethin film forming apparatus using laser, the laser beam irradiatingmeans emits pulse laser beams, and it includes means for controlling thepulse laser such that one position on the target may not be irradiatedwith a plurality of pulses of the laser beam within one second.

Therefore, new substance is not deposited by the next laser pulseirradiation until the crystal has sufficiently grown, and thereforeuniform film formation can be carried out with superior film quality.

In accordance with the sixth aspect of the present invention, the thinfilm forming apparatus using laser includes a plurality of targets eachhaving an aperture through which laser beam passes, and means forchanging positions of the targets, so that by changing positions ofthese targets, the laser beams can pass through an aperture of a targetto be incident on another target.

Therefore, plumes can be generated from a plurality of targets, only byintroducing one laser beam to the chamber. Consequently, a thin film canbe formed on a substrate surface of a large area without the necessityof means for changing optical path of the laser beam.

As the means for changing the position of the targets, means forrotating the targets may be used.

In the present invention, preferably, the targets and the substrate, arepositioned such that the distance between the position of laser beamsirradiation at the target and the substrate, for each target is thesame.

In accordance with the seventh aspect of the present invention, in thethin film forming apparatus using laser, the laser beam is directed tothe target with an incident angle θ which satisfies the followingcondition: when film is formed over a length x on the target for a timeperiod t of 0 to t₀ where the rate of elimination (dy/dt) of the targetin the depth direction y is represented as b (t), the value provided bytime integration of b (t) from t=0 to t=t₀ divided by tan (90°- θ)results in x or smaller.

In the thin film forming apparatus using laser, since the laser beam isdirected to the target with an incident angle θ which satisfies thecondition that the value obtained by time integral of d (t) from t=0 tot=t₀ divided by tan (90°- θ) results in x or smaller, the plume can begenerated from the target within the range of the length x only byintroducing one laser beam into the chamber. As a result, a thin filmcan be formed on a substrate surface of a large area, without changingoptical path of the laser beam.

According to an eighth aspect of the present invention, the thin filmforming apparatus using laser includes means for irradiating a pluralityof different positions on the target with a plurality of laser beams.

Therefore, film formation proceeds in parallel at a plurality ofpositions on the substrate, and therefore a thin film can be formed overa wide area without moving the substrate over a wide range.

The means for irradiating a plurality of laser beams preferably includesmeans for dividing one laser beam into a plurality of laser beams andfor directing the laser beams to different positions on the target.

According to a ninth aspect of the present invention, in the thin filmforming apparatus using laser, the surface of the target which isirradiated with the laser beam has prescribed unevenness.

Therefore, a plurality of plumes are generated in various directionsbecause of such nature of the plume that it generates in the directionof the normal of the target surface. Consequently, a thin film can beformed over wider range.

In accordance with the tenth aspect of the present invention, the thinfilm forming apparatus using laser includes means for linearly movingthe target in a direction perpendicular to that surface of the substrateholding means which holds the substrate.

Since the thin film forming apparatus using laser includes means forirradiating the target with a plurality of laser beams and means forlinearly moving the target in a direction perpendicular to the substrateholding surface of the substrate holding means, a plurality of positionsof laser beam irradiation on the target change on the target surface,and a plurality of plumes are generated at various positions on thesubstrate surface placed opposing to the target. Consequently, a thinfilm of high quality can be formed uniform on the substrate having largearea.

In accordance with the eleventh aspect of the present invention, thethin film forming apparatus using laser includes a plurality of targetsand means for moving the plurality of targets.

Since the thin film forming apparatus using laser includes means formoving a plurality of targets, plumes having a prescribed densitydistribution can be brought into contact uniformly with the substratesurface, and therefore a thin film having uniform film quality can bevapor-deposited over a wide area.

In accordance with the twelfth aspect of the present invention, the thinfilm forming apparatus using laser includes means for dividing one laserbeam into a plurality of beams and for irradiating different positionsof the target by respective ones of the divided laser beams.

Therefore, a plurality of portions of the target can be irradiated withthe laser beam simultaneously and efficiently, without increasing thelaser light source.

In accordance with the thirteenth aspect of the present invention, thethin film forming apparatus using laser includes film quality monitoringmeans which scans the substrate surface by laser beam irradiation andmeasuring the reflected light by means of a CCD camera for monitoringthe state of the film deposited on the substrate surface on real timebasis, and means for feeding back the result of monitoring by the filmquality monitoring means to the film forming conditions.

Since the thin film forming apparatus using laser includes film qualitymonitoring means for measuring laser beam reflected from substratesurface by a CCD camera and for monitoring on real time basis thecondition of the deposited film, and means for feeding back the resultmonitored by the film quality monitoring means to the film formingconditions, the film forming condition can be controlled to be optimizedduring the step of film formation as needed, and hence a thin film canbe formed over a wide area with superior quality.

In accordance with the fourteenth aspect of the present invention, inthe thin film forming apparatus using laser, the diameter and theincident angle of the laser beam are set such that the laser beamirradiates at least the foot of a common normal of the laser irradiationsurface of the target and the surface of the substrate.

In the thin film forming apparatus using laser, since the target hascircular or polygonal cross sectional shape and the incident angle andthe diameter of the laser beam are set such that the laser beamirradiates at least the foot of the common normal of the laserirradiation surface of the target and the surface of the substrate, anumber of normals of the target are included in the range of laser beamirradiation, and as a result, compared with a planar shaped target,plumes can be scattered in wider angles.

According to a fifteenth aspect, in the thin film forming apparatususing laser, the laser irradiation surface of the target is arrangedparallel to and facing the substrate surface, and the laser beamirradiating means emits the laser beam approximately perpendicular tothe target irradiation surface, with the beam passing through a lighttransmitting aperture provided approximately at the center of thesubstrate holding means.

In the thin film forming apparatus using laser, the laser irradiatingsurface of the target is placed parallel to and opposing to thesubstrate surface, and the laser beam irradiating means emits the laserbeams approximately perpendicular to the surface of the target throughan optical transmitting aperture provided approximately at the center ofthe substrates holding means, so that the extent of the plume generatedfrom the target can be maximized. This is because the fact that theextent of a plume generated from the target becomes larger as theincident angle of the laser beam is smaller, that is, the angle ofinclination from the direction of the normal of the target surfacebecomes smaller.

In accordance with the sixteenth aspect of the present invention, in thethin film forming apparatus using laser, the position of focus of thelaser beam emitted from the laser beam irradiating means is set to be onlaser irradiating surface of the target.

In the thin film forming apparatus using laser, the laser beams arecondensed such that the point of focus of the laser beams is positionedjust on the surface of the target, whereby the extent of the plumegenerated from the target can be made larger, so as to enable thin filmformation over wider area efficiently.

In accordance with the seventeenth aspect of the present invention, thethin film forming apparatus using laser includes local evacuating meansfor locally evacuating gas near that position of the chamber at whichthe plume is generated. By this structure, the degree of vacuum can bemaintained constant in wider region near the target, so that the regionwhere the plume is generated can be enlarged. Consequently, the area onthe substrate surface where excited atoms and ions in the plume reachcan be enlarged, so that the area on which uniform thin film can beformed, is enlarged.

In accordance with an eighteenth aspect of the present invention, thethin film forming apparatus using laser includes means for applying amagnetic field in the space between the target and the substrate.

In the thin film forming apparatus using laser, a cusp magnetic field isapplied to the space between the target and the substrate, and thereforeelectrons and ions in the plume which have been generated and scatteredat the portion of the target surface which is irradiated with the laserbeam tend to extend along the magnetic lines of force. Consequently, theplume spreads in the radial direction, and accordingly, uniform thinfilm can be formed over wider area of the substrate surface by a singleplume.

In accordance with the nineteenth aspect of the present invention, thethin film forming apparatus using laser includes means for supplyinghydrogen ions and hydrogen radicals to the surface of the substrate.

In the thin film forming apparatus using laser, since hydrogen ions andhydrogen radicals are applied to the surface of the substrate, surfacemigration of atoms and molecules at the surface of the substrate wherethe film grows can be promoted, and therefore a thin film havingsuperior crystal property with less point defects and less latticedefects can be formed.

In accordance with the twentieth aspect of the present invention, thethin film forming apparatus using laser includes a nozzle for blowinggas to the surface of the substrate, and means for directing the laserbeams to the target through the nozzle.

Therefore, the gas in the nozzle is activated by the laser beam, andtherefore activated gas can be supplied to the substrate surface.Different from ion beams of activated ion seeds which are accelerated byvoltage, the gas activated by the laser beam do not cause damage to thesubstrate, and therefore a thin film having high quality can be formed.

In accordance with the twenty-first aspect of the present invention, thethin film forming apparatus using laser includes a mesh electrodepositioned movable between the substrate and the target.

Therefore, it is possible to clean the substrate by causing dischargebetween the mesh electrode and the substrate surface before thin filmformation.

In accordance with the twenty-second aspect of the present invention,the thin film forming apparatus using laser includes at least one of RFsputtering means, DC sputtering means and ion beam sputtering means.

Therefore, a DC voltage or a high frequency voltage can be applied aspre-processing of the substrate and the target or as an assistance tothe laser beam. For example, by applying a high frequency voltage to thesubstrate or the target, the surface of the substrate or the target canbe made clean. When a DC voltage or a high frequency voltage is appliedor ion beam sputtering is used to assist the laser beam, the rate offilm formation can be improved, and thin film can be formed uniform overwider area.

According to a twenty-third aspect of the present invention, the thinfilm forming apparatus using laser includes a high frequency indicationcoil for generating a high frequency induction field near the target.

Since the thin film forming apparatus using laser includes a highfrequency induction coil near the target and a high frequency inductionfield is generated near the target for generating plasma caused bydischarge near the target, some energy can be applied to the surface ofthe target. Consequently, even when the energy density of the laserbeams is low, generation of plume is facilitated.

According to a twenty-fourth aspect of the present invention, the thinfilm forming apparatus using laser includes means for irradiatinginfrared laser or far infrared laser to the surface of the substrate,and means for cooling the substrate.

Therefore, it becomes possible to locally heat portions of the substrateas needed, and rise of temperature at portions where heating isunnecessary can be prevented.

According to a twenty-fifth aspect of the present invention, the thinfilm forming apparatus using laser includes means for irradiatingradiation beam to the substrate surface.

In the thin film forming apparatus using laser, since radiation beam isapplied to the surface of the substrate, the electronic state of theatoms near the substrate surface are resonantly excited innon-equilibrium, and they reached the substrate surface so that theatoms, molecules and clusters of the target raw material are resonantlyexcited in non-equilibrium, whereby crystallization of the target rawmaterial in the form of atoms, molecules or clusters on the substratesurface can be promoted not in thermal equilibrium, so that thin filmcan be formed with high quality at lower temperature of film formation.

According to a twenty-sixth aspect of the present invention, the thinfilm forming apparatus using laser includes a movable mirror enablingthe laser beam irradiating means to direct the laser beams forirradiating the target also to the surface of the substrate.

Since the thin film forming apparatus using laser includes means forenabling irradiation of the substrate surface with the laser beam whichis for irradiating the target, the substrate surface can be heated bythe laser beam and cleaned easily at low cost.

According to a twenty-seventh aspect of the present invention, the thinfilm forming apparatus using laser includes means for introducingactivated oxidizing gas into the chamber.

Therefore, oxygen defect generated during film deposition can berepaired immediately by oxygen ions supplied from the activatedoxidizing atmosphere. Therefore, at a relatively low substratetemperature, an oxide film with superior crystal property with lessoxide defects can be obtained, and therefore degradation of thesubstrate derived from high temperature of film formation anddegradation of thin film function caused by induced undesirable sidereaction can be prevented. Further, since the activated oxidizing gasintroduced in the chamber does not have such a high kinetic energy asion beams, the damage to the substrate is negligible.

According to a twenty-eighth aspect of the present invention, the thinfilm forming apparatus using laser includes means for activating theoxidizing gas by silent discharge.

Since the thin film forming apparatus using laser includes means forintroducing activated oxidizing gas in the chamber by silent discharge,ions are eliminated rapidly by impingement with the activated oxygengas, and therefore active oxygen atoms having relatively lowreactiveness are maintained at high concentration and applied to thesubstrate. Therefore, oxidation on the substrate surface is promoted.

In accordance with the twenty-ninth aspect of the present invention, thethin film forming apparatus using laser includes means for applying DCpotential or RF potential to the substrate.

In the thin film forming apparatus using laser, since DC potential or RFpotential is applied to the substrate, the oxidizing gas which have beenionized near the plume by the reaction with the radical seeds or thelike in the plume reaches the substrate surface with appropriate energy.Such ion seeds repair oxygen defects generated during deposition of thefilm, and therefore an oxide film having superior property of crystalwith less oxygen defect can be obtained even at a relatively lowsubstrate temperature.

According to thirtieth aspect of the present invention, the thin filmforming apparatus using laser includes means for detecting the state ofthe target surface by monitoring scattered light of the laser beamsdirected to the target.

Since the state of the surface of the target is detected by monitoringthe scattered light of the laser beams with which the target isirradiated, the state of the target surface can be detected on real timebasis during the process for forming the thin film, which can be fedbackto optimize the film forming conditions.

In accordance with thirty-first aspect of the present invention, thethin film forming apparatus using laser includes means for detectingcomposition of the target by detecting characteristic x-ray generated byirradiating the portion of the target which is irradiated with the laserbeam, with x-ray or electron ray.

In the thin film forming apparatus using laser, since the composition ofthe target is detected by detecting the characteristic x-ray generatedby irradiating the region of the target which is irradiated with thelaser beam, with x-ray or electron ray, the composition of the target inthe laser beam sputtering region can be detected on real time basisduring the process for forming the thin film.

According to a thirty-second aspect of the present invention, the thinfilm forming apparatus using laser includes means for detecting thelaser beam reflected at the film forming surface of the substrate andfor measuring film thickness by polarization analysis of the laser beam.

In the thin film forming apparatus using laser, since the laser beamreflected from the substrate surface is detected and the film thicknesscan be measured by polarization analysis of the laser beam, thedistribution of the film thickness formed over the substrate surface canbe monitored on real time basis during the process for forming the thinfilm.

According to a thirty-third aspect of the present invention, the thinfilm forming apparatus using laser includes measuring means formeasuring component and nature of the plume, analyzing means foranalyzing the information obtained by the measuring means, and controlmeans for controlling film forming parameters based on the result ofanalysis obtained by the analyzing means.

In the thin film forming apparatus using laser, since the informationobtained by measuring means for measuring nature and component of theplume generated from the target is analyzed and the film formingparameters are controlled based on the result of analysis, the filmforming parameters can be monitored at the site during the process forfilm formation, and optimal conditions for film formation can beobtained by feedback control.

According a thirty-fourth aspect of the present invention, the thin filmforming apparatus using laser includes plume monitoring means formonitoring position of the plume, control means for processing the datamonitored by the plume monitoring means and for outputting a controlsignal, and means for adjusting position or size of the plume based onthe output signal from the control means.

Since the thin film forming apparatus using laser includes control meansfor processing data monitored by the plume monitoring means and foroutputting a control signal and means for adjusting position or size ofthe plume based on the output signal from the control means, thepositional relation between the plume and the target can be checkedoptimally, and therefore uneven film quality caused by displacement ofthe plume can be prevented.

According to a thirty-fifth aspect of the present invention, in the thinfilm forming apparatus using laser, the target is arranged such that thecentral axis of the plume forms a prescribed angle of inclination withrespect to the substrate surface and crosses near an end portion of thesubstrate surface.

Therefore, the area of contact between the substrate surface and theplume can be made larger, and, by rotating the surface in a planeparallel to its surface, the film deposition on the substrate surfacecan be made uniform.

According to a thirty-sixth aspect of the present invention, in the thinfilm forming apparatus using laser, the surface of the target which isto be irradiated with the laser beam and the substrate surface arearranged such that the surfaces are both substantially vertical and thesurfaces oppose to each other with a prescribed angle of inclination.

In the thin film forming apparatus using laser, since the target and thesubstrate surfaces are arranged such that these two are substantiallyvertical and opposed to each other with a prescribed angle, foreignmatters generated near the target and near the substrate surface falldownward, and therefore thin film can be formed with foreign matters notmuch adhered on the surface of the substrate.

According to a thirty-seventh aspect of the present invention, the thinfilm forming apparatus using laser includes means for emitting aplurality of laser beams having different wavelengths.

In the thin film forming apparatus using laser, since the laser beamirradiating means emit a plurality of laser beams having differentwavelengths, it becomes possible to irradiate the surface of the targetwith laser beam having long wavelength so that the target surface isbrought to melted or about to be melted state, which contributes toreduce surface roughness of the target.

According to a thirty-eighth aspect of the present invention, the thinfilm forming apparatus using laser includes first and second laser thinfilm forming means which can form thin films on the substrate surfaceindependent from each other, and means for conveying the substratebetween the first and second laser thin film forming means.

Therefore, it becomes possible to form respective layers in separatechambers when two-layered thin film having different conditions for filmformation is to be formed, and therefore respective thin films can beformed successively, continuously and rapidly without changing theconditions for film formation in each of the laser thin film formingmeans. Consequently, the thin film can be formed without degrading thefunction of the finished thin film.

According to a thirty-ninth aspect of the present invention, the thinfilm forming apparatus using laser includes a first laser thin filmforming means constituting a preliminary thin film forming means forforming a metal thin film, and a second thin film forming meansconstituting a primary thin film forming means for forming a thin filmof metal oxide.

In the thin film forming apparatus using laser, since a metal thin filmis preliminary formed in the first laser thin film forming means and ametal oxide is formed by the second laser thin film forming means, anunderlaying layer having superior crystal structure can be provided bythe preliminary formation of a metal thin film. Therefore, in thesubsequent step of forming thin film of metal oxide, a prescribed goodcrystal structure can be obtained even at a relatively low temperature.

According to a fortieth aspect of the present invention, in the thinfilm forming apparatus using laser, the target has mutually opposinginner surfaces so that the incident laser beam can be reflected for aplurality of times.

Therefore, plumes can be generated at a plurality of portions of thetarget by one laser beam, and therefore thin film can be formed overwider area of the substrate without increasing the number of components.

According to a forty-first aspect of the present invention, the thinfilm forming apparatus using laser includes means for activating neutralparticles in the plume between the target and the substrate.

Therefore, neutral particles in the form of atoms, molecules or clustersin the plume generated at the portion of the targets surface which isirradiated with laser can be ionized. By applying electric field to theparticles serving as the raw material of the thin film thus ionized, thekinetic energy when the particles are directed to the substrate can befreely controlled, and therefore the damage to the substrate can beprevented and the temperature of the substrate necessary forcrystallization of the thin film can be made lower.

According to a forty-second aspect of the present invention, the thinfilm forming apparatus using laser includes means for supplying electronbeam and hydrogen radicals to the cluster of atoms and ions included inthe plume.

Therefore, the cluster of atoms included in the plume can be removed anddissolved, and the ionic particles can be neutralized. As a result, athin film having a stacked structure with shaft interface can be formed.

According to a forty-third aspect of the present invention, the thinfilm forming apparatus using laser includes means for applying magneticfield at least to the vicinity of the target.

In the thin film forming apparatus using laser, since a magnetic fieldis applied at least to the vicinity of the target, movement of chargedparticles such as ions and electrons in the plume are influenced by themagnetic field, so that the charged particles drift in the direction ofthe magnetic lines of force. Therefore, by applying a magnetic fieldsuch that the magnetic lines of force do not pass the surface of thesubstrate, the amount of ions in the plume incident on the substrate canbe controlled and suppressed. Meanwhile, non-charged particles such asneutral atoms and clusters in the plume are not influenced by themagnetic field so that these particles reach the substrate and aredeposited thereon.

According to a forty-fourth aspect of the present invention, the thinfilm forming apparatus using laser includes shielding means forpartially shielding the plume between the target and the substrate.

Therefore, a portion of the plume can be arbitrarily shielded, andtherefore spatial distribution of the density of particles constitutingthe plume in contact with the substrate can be made uniform.

According to a forty-fifth aspect of the present invention, the thinfilm forming apparatus using laser includes atom capturing meansprovided detachably, surrounding a point of laser irradiation andvicinity thereof on the laser radiation surface of the target.

Therefore, generation of dusts in the chamber can be suppressed, whichallows continuous film forming processes for a long period of time,which in turn leads to improved production yield.

According to a forty-sixth aspect of the present invention, the thinfilm forming apparatus using laser includes a plurality of plates eachhaving an opening through which a laser beam can pass, between thetarget and a window transmitting the laser beam.

Therefore, the transmitting window can be shielded by the plates againstthe substance scattered from the target, and therefore deposition on thewindow can be suppressed.

According to a forty-seventh aspect of the present invention, the thinfilm forming apparatus using laser provides another window transmittingthe laser beam between the aforementioned window transmitting the laserand the target, and has means for moving the position of laser beamtransmission at the said another window.

In the thin film forming apparatus using laser, since an additionalwindow through which laser beam is transmitted is provided between thelaser transmitting window and the target and the position of laser beamtransmission of the additionally provided window is moved, theadditional window prevents the dust scattered from the target fromreaching the outer laser transmitting window, so that the deposition onthe outer window can be prevented.

According to a forty-eighth aspect of the present invention, the thinfilm forming apparatus using laser includes a grid through which thelaser beam can transmit between the laser transmitting window and thetarget.

Therefore, the substance scattered from the plume can be prevented fromreaching the window, and therefore deposition on the window can beprevented.

According to a forty-ninth aspect of the present invention, the thinfilm forming apparatus using laser includes a nozzle having an openingthrough which the laser beam can pass, between the laser beamtransmitting window and the target.

Therefore, dust and substances scattered from the plume can be preventedfrom reaching the window, and therefore deposition on the window can beprevented.

According to a fiftieth aspect of the present invention, the thin filmforming apparatus using laser includes a shutter which is opened onlyduring laser beam irradiation, provided between the laser transmittingwindow and the target.

Therefore, the dust scattered from the target which is generallygenerated after laser radiation can be shielded by the shutter beforereaching the window. Therefore, deposition on the window can beprevented.

According to a fifty-first aspect of the present invention, the thinfilm forming apparatus using laser includes a gate for keeping airtightseal between the laser beam transmitting window and the target and meansfor supplying and exhausting gas to and from the space between the laserbeam transmitting window and the target.

Since the thin film forming apparatus using laser includes a gate forkeeping airtight seal between the laser beam transmitting window and thetarget and means for supplying and evacuating gas to and from the spacebetween the laser beam transmitting window and the gate, the window canbe changed without exposing most part of the chamber to the atmosphere.

According to fifty-second aspect of the present invention, the thin filmforming apparatus using laser includes an optical transmission path theinside of which can be held airtight provided between the laser beamtransmitting window and the laser beam irradiating means, and the insideof optical transmission path is filled with a prescribed gas or keptvacuum.

Since the inside of the optical transmission path is filled with aprescribed gas or kept vacuum in the thin film forming apparatus usinglaser, the laser beam can be passed without any attenuation during thepassage through the optical transmission path, and the inner wall of theoptical transmission path can be kept clean.

According to a fifty-third aspect of the present invention, in the thinfilm forming apparatus using laser, the incident angle of the laser beamdirected to the target with respect to the target surface is set to beat least 30° with respect to the direction of the normal of the laserirradiation surface of the target.

Therefore, the direction of generation of the plume is off the directionof the laser transmitting window, and therefore deposition of substancesincluded in the plume on the window can be suppressed, and thusdeposition on the window can be prevented.

According to a fifty-fourth aspect of the present invention, the thinfilm forming apparatus using laser includes a mirror arranged to reflectthe incident laser beam in the chamber to direct the laser beam towardthe window.

In the thin film forming apparatus using laser, since the laser beamincident in the chamber is reflected to be directed to the window, thesubstance deposited on the window can be removed.

According to a fifty-fifth aspect of the present invention, the thinfilm forming apparatus using laser includes second laser beamirradiating means for irradiating the laser transmitting window with thelaser beam, monitoring means for monitoring the frost on the window bythe laser beam emitted from the second laser beam irradiating means,means for removing the frost of the window by blowing purging gas to thewindow, and control means for operating the means for removing the froston the window based on the result of monitoring by the monitoring meansfor monitoring the frost on the window.

In the thin film forming apparatus using laser, since the frost on thewindow is monitored and the frost is removed by blowing purge gas whenthe window is frosted, the frost on the laser transmitting window isalways prevented, and therefore the film can be formed under constantcondition.

According to a fifty-sixth aspect of the present invention, in the thinfilm forming apparatus using laser, the target is divided into aplurality of targets, each divided target including metallurgicalsubstance of different compositions, and the laser irradiating meansincludes means for adjusting position of laser beam irradiation on thedivided target. Consequently, thin films of a plurality of metallurgicalsubstances of different components can be formed.

In the thin film forming apparatus using laser, since laser beam isdirected to a plurality of divided targets including metallurgicalsubstances of different components, when thin films of a plurality ofdifferent compositions are to be formed on the substrate, the ratio ofthe components can be changed or adjusted relatively easily.

According to a fifty-seventh aspect of the present invention, in thethin film forming apparatus using laser, the target has a depressedportion on the surface which is to be irradiated with the laser beam.

Therefore, internal stress caused by the difference in thermal expansioncoefficient or the difference in temperature can be dispersed, andgeneration and development of cracks caused by the pulse shock can besuppressed. Further, since the depressed portion is provided, the areaof laser absorption on the laser irradiation surface can be increased.

As described above, by the thin film forming apparatus using laser inaccordance with the present invention, a uniform thin film havingsuperior quality can be formed efficiently over wider area withoutdamaging the substrate.

Tarnish or deposition of the laser inlet window during the process forforming the thin film can be prevented, and therefore the laser beam canbe directed to the target to generate the plumes under constantcondition.

Further, the film forming conditions can be optimized by real timecontrol during the process for forming the thin film, and thereforecontrol of the composition of the thin film to be formed or the like canbe surely and easily carried out.

Since the present invention has these effects, the production yield informing a thin film on the substrate surface can be significantlyimproved.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the manner of laser beamirradiation on the target and generation of a plume in accordance withthe first embodiment of the present invention.

FIG. 2 is an illustration showing relation between intensitydistribution of the laser beam and the intensity distribution of theplume in accordance with the embodiment shown in FIG. 1.

FIG. 3 shows an example of an optical system for obtaining a laser beamhaving annular light intensity distribution.

FIG. 4 is a perspective view of a conical axicone as an element forchanging direction of the light beam.

FIG. 5 is a perspective view showing an example of a prism as an opticalsystem for obtaining a desired light intensity distribution.

FIG. 6 shows a number of axicone or prisms aligned.

FIG. 7 shows a manner of dividing a laser beam into a number of specificdirections by using a diffraction grating.

FIG. 8 shows a manner of scanning by a laser beam having annular orcircular light intensity distribution.

FIG. 9 shows a manner of scanning by a laser beam having linear lightintensity distribution.

FIG. 10 shows a manner of scanning by the laser beam having dot-shapedlight intensity distribution.

FIG. 11 shows a manner of scanning by the laser beam having lightintensity distribution in the form of a set of points.

FIG. 12 shows an example of an instable type resonator for forming alight intensity distribution in advance in a laser unit.

FIG. 13 shows an example in which an apertured reflection mirror is usedas a partial reflection mirror of the laser unit.

FIG. 14 is a cross section showing a schematic structure of a thin filmforming apparatus using laser in accordance with the second embodimentof the present invention.

FIG. 15A shows a manner of converting cross section of a beam on thetarget to a square, by controlling incident angle of the laser beam withrespect to the target, and FIG. 15B shows cross sectional shape of thelaser beam.

FIG. 16A is a schematic diagram of an apparatus for changing crosssectional shape of the laser beam by using a beam shape convertingelement, and FIGS. 16B and 16C show cross sectional shapes of the laserbeam in enlargement, at the cross section taken along the line B--B andC--C of FIG. 16A.

FIG. 17 is a schematic diagram of an apparatus for changing the crosssection of the beam on the target to a square by using a cylindricallens.

FIG. 18 is a schematic diagram of an apparatus for moving position ofirradiation of the target with the laser beam, employing a movablecondenser lens.

FIG. 19 is a schematic diagram of an apparatus for moving position ofirradiation of the target with the laser beam employing a movablepartial reflection mirror in an optical resonator in the laser unit.

FIG. 20 is a cross sectional view showing schematic structure of a thinfilm forming apparatus using laser in accordance with the thirdembodiment of the present invention.

FIG. 21 is a cross section showing a schematic structure of a thin filmforming apparatus using laser in accordance with the fourth embodimentof the present invention.

FIG. 22 is a cross sectional view showing schematic structure of a thinfilm forming apparatus in accordance with the fifth embodiment of thepresent invention.

FIG. 23 is a perspective view showing schematic structure of the thinfilm forming apparatus using laser in accordance with the sixthembodiment of the present invention.

FIGS. 24A and 24B show two examples of divided type adaptive mirror usedin the sixth embodiment of the present invention.

FIG. 25 is a perspective view showing a schematic structure of the thinfilm forming apparatus using laser in accordance with the seventhembodiment of the present invention.

FIG. 26 is a cross section showing schematic structure of the thinforming apparatus using laser in accordance with the eighth embodimentof the present invention.

FIG. 27 is a cross section showing schematic structure of the thin filmforming apparatus using laser in accordance with the ninth embodiment ofthe present invention.

FIG. 28 is a cross section showing a schematic structure of the thinfilm forming apparatus using laser in accordance with the tenthembodiment of the present invention.

FIG. 29 is an illustration showing change in the optical path lengthduring laser beam scanning.

FIG. 30 is a partially exploded perspective view showing a schematicstructure of the thin film forming apparatus using laser in accordancewith the eleventh embodiment of the present invention.

FIG. 31A is a cross sectional view showing schematic structure of thethin film forming apparatus using laser in accordance with the twelfthembodiment of the present invention in which laser beam 16 is reflectedby a mirror 112, and FIG. 31B is a cross section showing the schematicstructure of the apparatus when the laser beam 16 is reflected by amirror 113 having a reflection angle different from that of mirror 112.

FIG. 32 is a cross sectional view showing schematic structure of thethin film forming apparatus using laser in accordance with thethirteenth embodiment of the present invention.

FIGS. 33A and 33B show loci of plumes generated at the time of pulselaser scanning at a prescribed period, in which FIG. 33A shows anexample of circular scanning and FIG. 33B shows zigzag scanning.

FIG. 34 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thefourteenth embodiment of the present invention.

FIG. 35 is a perspective view showing a schematic structure of the thinfilm forming apparatus using laser in accordance with the fifteenthembodiment of the present invention.

FIG. 36 is a perspective view showing schematic structure of the thinfilm forming apparatus using laser in accordance with the sixteenthembodiment of the present invention.

FIG. 37 is a cross section showing a schematic structure of the thinfilm forming apparatus using laser in accordance with the seventeenthembodiment of the present invention.

FIG. 38 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theeighteenth embodiment of the present invention.

FIG. 39 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thenineteenth embodiment of the present invention.

FIG. 40 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with the twentiethembodiment of the present invention.

FIG. 41A is a cross sectional view showing one example of a silentdischarge apparatus used in the twentieth embodiment of the presentinvention, and FIG. 41B is a cross section taken along the line B--B ofFIG. 41A.

FIG. 42A is a cross sectional view showing another example of the silentdischarge apparatus used in the twentieth embodiment of the presentinvention, and FIG. 42B is a cross section taken along the line B--B ofFIG. 42A.

FIG. 43 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thetwenty-first embodiment of the present invention.

FIG. 44 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thetwenty-second embodiment of the present invention.

FIG. 45 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thetwenty-third embodiment of the present invention.

FIG. 46 is a section viewed from the top of a chamber of the thin filmforming apparatus using laser in accordance with the twenty-thirdembodiment of the present invention.

FIG. 47 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thetwenty-fourth embodiment of the present invention.

FIG. 48 is a cross section showing a schematic structure of a mainportion of the thin film forming apparatus using laser in accordancewith the twenty-fifth embodiment of the present invention.

FIG. 49 is a cross sectional view showing a schematic structure of themain portion of the thin film forming apparatus using laser inaccordance with the twenty-sixth embodiment of the present invention.

FIG. 50 is a cross sectional view showing a schematic structure of themain portion of the thin film forming apparatus using laser inaccordance with the twenty-seventh embodiment of the present invention.

FIG. 51 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thetwenty-eight embodiment of the present invention.

FIG. 52 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thetwenty-ninth embodiment of the present invention.

FIGS. 53A to 53C show shapes of target surfaces, wherein FIG. 53A showsan example in which half columns are arranged irregularly, FIG. 53Bshows an example in which triangular prisms or pyramids are arrangedregularly, and FIG. 53C shows an example in which triangular prisms orpyramids are arranged at random.

FIG. 54 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with the thirtiethembodiment of the present invention.

FIG. 55 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thethirty-first embodiment of the present invention.

FIG. 56 shows a manner of dividing a laser beam into a plurality ofbeams by using a total reflection mirror which can be used inthe-thirty-first embodiment of the present invention.

FIG. 57 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thethirty-second embodiment of the present invention.

FIG. 58 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thethirty-third embodiment of the present invention.

FIG. 59 is a cross sectional view showing a schematic structure of themain portion of the thin film forming apparatus using laser inaccordance with the thirty-fourth embodiment of the present invention.

FIG. 60 is an illustration showing relation between diameter D of thetarget and diameter ω of the laser beam in the thirty-fourth embodimentof the present invention.

FIG. 61 is a graph showing the relation between the angle of plumeextension, and the diameter D of the target and diameter ω of the laserbeam in the thirty-fourth embodiment of the present invention.

FIG. 62 is a cross sectional view showing a schematic structure of themain portion of the thin film forming apparatus using laser, when atarget having polygonal cross sectional shape is used in thethirty-fourth embodiment of the present invention.

FIG. 63 is a cross sectional view showing the state when a laser beam isemitted in the direction of the normal of the target surface, in thethirty-fourth embodiment of the present invention.

FIG. 64 is a cross sectional view showing the state when the laser beamis directed such that the point of focus of the beam is positioned nearan opening of the substrate, in the thirty-fourth embodiment of thepresent invention.

FIG. 65 is a perspective view showing the state when the laser beam isdirected to a columnar target through an opening provided at the centerof a dish shaped target, in the thirty-fourth embodiment of the presentinvention.

FIG. 66 is a perspective view showing a plurality of substrates fixed onthe lower surface of a dish shaped substrate holder having an opening atthe center, which can be used in the thirty-fourth embodiment of thepresent invention.

FIG. 67 is a perspective view showing an example of parallel movement ofthe target while rotating the same, in order to prevent reduction inextension angle of the plume caused by wear of the target, in thethirty-fourth embodiment of the present invention.

FIG. 68 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thethirty-fifth embodiment of the present invention.

FIG. 69 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thethirty-sixth embodiment of the present invention.

FIG. 70 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thethirty-seventh embodiment of the present invention.

FIG. 71 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thethirty-eighth embodiment of the present invention.

FIG. 72 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thethirty-ninth embodiment of the present invention.

FIG. 73 is cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with the fortiethembodiment of the present invention.

FIG. 74 is a cross sectional view showing a schematic structure of thethin film forming apparatus in accordance with the forty-firstembodiment of the present invention.

FIG. 75 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theforty-second embodiment of the present invention.

FIG. 76 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theforty-third embodiment of the present invention.

FIG. 77 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theforty-fifth embodiment of the present invention.

FIG. 78 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theforty-sixth embodiment of the present invention.

FIG. 79 is a graph showing relation between the number of films formedand the temperature of the targets, when the apparatus includes meansfor cooling the target and when it does not include such means, in theforty-sixth embodiment of the present invention.

FIG. 80 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theforty-seventh embodiment of the present invention.

FIG. 81 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theforty-eighth embodiment of the present invention.

FIG. 82 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theforty-ninth embodiment of the present invention.

FIG. 83 is a cross sectional view showing a modification of the thinfilm forming apparatus using laser in accordance with the forty-ninthembodiment of the present invention.

FIG. 84 is a cross sectional view showing another modification of thethin film forming apparatus using laser in accordance with theforty-ninth embodiment of the present invention.

FIG. 85 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with the fiftiethembodiment of the present invention.

FIG. 86 is a cross sectional view showing a modification of the thinfilm forming apparatus using laser in accordance with the fiftiethembodiment of the present invention.

FIG. 87 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thefifty-first embodiment of the present invention.

FIG. 88 is a cross sectional view showing a modification of the thinfilm forming apparatus using laser in accordance with the fifty-firstembodiment of the present invention.

FIG. 89 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thefifty-second embodiment of the present invention.

FIG. 90 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thefifty-third embodiment of the present invention.

FIG. 91 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thefifty-fourth embodiment of the present invention.

FIG. 92 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thefifty-fifth embodiment of the present invention.

FIG. 93A is a plan showing, in enlargement, a target used in the thinfilm forming apparatus using laser in the fifty-fifth embodiment of thepresent invention and FIG. 93B is a cross section taken along the lineB--B of FIG. 93A.

FIG. 94A is a plan view showing layout of target in one state at a mainportion of the thin film forming apparatus using laser in accordancewith the fifty-sixth embodiment of the present invention, FIG. 94B is afront view showing a schematic structure of the main portion of theapparatus at that state, FIG. 94C is a plan view showing layout of thetarget in another state, and FIG. 94D is a front view showing theschematic structure of the main portion of the apparatus at that state.

FIG. 95 shows a modification of the fifty-fifth embodiment of thepresent invention.

FIG. 96A is a plan view showing layout of the target in accordance witha modification of the fifty-sixth embodiment of the present invention,and FIG. 96B is a front view showing a schematic structure of the mainportion of the apparatus in this modification.

FIG. 97 is a cross section showing a schematic structure of the thinfilm forming apparatus using laser in accordance with anothermodification of the fifty-sixth embodiment of the present invention.

FIG. 98 shows an example in which a condenser lens having long focallength as compared with the distance between two targets is used in thefifty-fifth embodiment of the present invention.

FIG. 99 is an illustration showing the operation in the fifty-seventhembodiment of the present invention.

FIG. 100 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thefifty-eighth embodiment of the present invention.

FIG. 101 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thefifty-ninth embodiment of the present invention.

FIG. 102 is a cross sectional view showing a schematic structure of amain portion of the thin film forming apparatus using laser inaccordance with the sixtieth embodiment of the present invention.

FIG. 103 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thesixty-first embodiment of the present invention.

FIG. 104 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thesixty-second embodiment of the present invention.

FIG. 105 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thesixty-third embodiment of the present invention.

FIG. 106 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thesixty-fourth embodiment of the present invention.

FIG. 107 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thesixty-fifth embodiment of the present invention.

FIG. 108 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thesixty-sixth embodiment of the present invention.

FIG. 109 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thesixty-seventh embodiment of the present invention.

FIG. 110 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thesixty-eighth embodiment of the present invention.

FIG. 111 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with thesixty-ninth embodiment of the present invention.

FIG. 112 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theseventieth embodiment of the present invention.

FIG. 113 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theseventy-first embodiment of the present invention.

FIG. 114 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theseventy-second embodiment of the present invention.

FIG. 115 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theseventy-third embodiment of the present invention.

FIG. 116 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theseventy-fourth embodiment of the present invention.

FIG. 117 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theseventy-fifth embodiment of the present invention.

FIG. 118 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theseventy-sixth embodiment of the present invention.

FIG. 119 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aseventy-seventh embodiment of the present invention.

FIG. 120 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theseventy-eighth embodiment of the present invention.

FIG. 121 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aseventy-ninth embodiment of the present invention.

FIG. 122 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with an eightiethembodiment of the present invention.

FIG. 123 is a cross sectional view showing a schematic structure of onemodification of the thin film forming apparatus using laser inaccordance with an eightieth embodiment of the present invention.

FIG. 124 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aneighty-first embodiment of the present invention.

FIG. 125 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aneighty-second embodiment of the present invention.

FIG. 126 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aneighty-third embodiment of the present invention.

FIG. 127 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aneighty-fourth embodiment of the present invention.

FIG. 128 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aneighty-fifth embodiment of the present invention.

FIG. 129 is an illustration showing the manner of movement of chargedparticles in the plume near the surface of the target, in the thin filmforming apparatus using laser in accordance with the eighty-fifthembodiment of the present invention.

FIG. 130 is a is a cross sectional view showing a schematic structure ofthe thin film forming apparatus using laser in accordance with aneighty-sixth embodiment of the present invention.

FIG. 131 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aneighty-seventh embodiment of the present invention.

FIG. 132 is a cross sectional view showing a schematic structure of themain portion of one modification of the thin film forming apparatususing laser in accordance with the eighty-seventh embodiment of thepresent invention.

FIG. 133 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aneighty-eighth embodiment of the present invention.

FIG. 134A is a cross sectional view showing a schematic structure of themain portion of the thin film forming apparatus using laser inaccordance with an eighty-ninth embodiment of the present invention,FIG. 134B shows, in enlargement, an aperture used in the apparatus ofFIG. 134A, FIG. 134C shows, in enlargement, a mesh grid used in theapparatus of FIG. 134A, and FIG. 134D is a perspective view showing, inenlargement, the shape of a lattice-like elongate grid used in theapparatus of FIG. 134A.

FIG. 135 is a cross sectional view showing a schematic structure of themain portion of one modification of the thin film forming apparatususing laser in accordance with the eighty-ninth embodiment of thepresent invention.

FIG. 136 is a cross sectional view showing a schematic structure of themain portion of another modification of the thin film forming apparatususing laser in accordance with the eighty-ninth embodiment of thepresent invention.

FIG. 137 is a cross sectional view showing a schematic structure of themain portion of a still another modification of the thin film formingapparatus using laser in accordance with the eighty-ninth embodiment ofthe present invention.

FIG. 138 is a cross sectional view showing a schematic structure of themain portion of a still further modification of the thin film formingapparatus using laser in accordance with the eighty-ninth embodiment ofthe present invention.

FIG. 139 is a cross sectional view showing a schematic structure of themain portion of a still further modification of the thin film formingapparatus using laser in accordance with the eighty-ninth embodiment ofthe present invention.

FIG. 140 is a cross sectional view showing a schematic structure of themain portion of a still further modification of the thin film formingapparatus using laser in accordance with the eighty-ninth embodiment ofthe present invention.

FIG. 141 is a cross sectional view showing, in enlargement, the shape ofthe vicinity of the target used in the thin film forming apparatus usinglaser in accordance with a ninetieth embodiment of the presentinvention.

FIG. 142 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aninety-first embodiment of the present invention.

FIG. 143 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aninety-second embodiment of the present invention.

FIG. 144 is a perspective view showing irradiation of laser beambridging two portions of a target which is divided into concentric twoportions, in the thin film forming apparatus using laser in accordancewith the ninety-second embodiment of the present invention.

FIG. 145 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with theninety-third embodiment of the present invention.

FIG. 146 is a perspective showing irradiation of laser beam reachingthree portions of a target divided into concentric three portions, inthe thin film forming apparatus using laser in accordance with theninety-third embodiment of the present invention.

FIG. 147 is a cross sectional view showing a schematic structure of thethin film forming apparatus using laser in accordance with aninety-fourth embodiment of the present invention.

FIG. 148 is a cross sectional view showing a schematic structure of aconventional thin film forming apparatus using laser disclosed inJapanese Patent Laying-Open No. 4-452263.

FIG. 149 is a cross sectional view showing a schematic structure ofanother conventional thin film forming apparatus using laser disclosedin Japanese Patent Laying-Open No. 4-114904.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention and a modification thereofwill be described. Referring to FIG. 1, in the apparatus of thisembodiment, when a target 5 is irradiated with a laser beam 16,molecules constituting the target are evaporated to generate a plume 15,which is like a frame of a candle. The plume is generated extendingapproximately in the direction of the normal of the target. However, theextension of the plume is small, and therefore when a film is formed byusing this plume, the resulting film thickness distribution is inproportion to the intensity distribution of the plume.

FIG. 2 is an illustration showing the relation between the intensitydistribution of the laser beam and the intensity distribution of theplume. In the figure, the intensity distribution of the plumesrepresented by the dotted lines each corresponds to one annular beam,and when the two plumes represented by the two dotted lines areoverlapped, a plume having a flat portion of the intensity distributionsuch as represented by the solid line in the figure can be obtained. Thesize of the plume differs dependent on the material of the target and onthe energy of laser for irradiation. Therefore, it is necessary toadjust the diameter of the annular beam or to adjust in advance thelaser output so that the flat portion become wide enough.

In FIG. 1, the intensity distribution of the beam is annular. Theintensity distribution may be comb-shaped, a grid or a set of points. Inany case, light intensity per unit area can be increased as comparedwith a case where the plume is enlarged by enlarging the diameter of thelaser beam, and therefore the efficiency of plume generation can beincreased. In addition, the flat portions of the intensity distributionof the plume can be widened, and therefore a film can be deposited onwider area with small variation in film thickness distribution.

FIG. 3 shows an example of an optical system for obtaining a beam havingappropriate distribution. The intensity distribution of a common laserbeam 16 is of gauss type or has a top hat shaped. Therefore, at first,the laser beam 16 is passed through an element 4200 for changing thedirection of the light. In this example, this element is a prism asshown in the figure. After passing through the element for changing thedirection, the beam is divided into two and at the same time, thedirection thereof is changed. When the light is condensed by using aspherical lens as a condenser lens 9, the light will be focused as twopoints at the point of focus. When a cylindrical lens is used as thecondenser lens 9, the light provides two parallel lines. By utilizingthe element for changing the direction of the light and the condenserlens, an arbitrary intensity distribution can be obtained. In order toobtain an appropriate distribution, part of the laser beam may beintercepted by providing an annular or linear aperture in a mask.However, use of the element for changing the direction of the mask isadvantageous in that the loss of light caused by interception can beavoided.

FIG. 4 shows a conical axicone 4201 used as the element 4200 forchanging the directions of light. In this example, the direction of thebeam is converted in axial symmetry, and therefore when focused, thebeam will be annular. FIG. 5 shows an example employing a prism 4202.FIG. 6 shows a number of axicones 4201 or prisms 4202 aligned, whichallows provision of a number of lines or annuli. FIG. 7 shows an examplein which a diffraction grating 4204 is used, which can separate a laserbeam 16a into a number of specific directions. A common diffractiongrating having parallel groups or concentric groups may be used as thegrating 4204. Though a transmitting type diffraction grating is usedhere, a reflecting type one may be used.

FIGS. 8 to 11 show manners of scanning such of points of focus. When athin film is to be formed uniform over wider area, scanning of thesurface of substrate 2 by moving substrate 2 or laser beam 16 isnecessary. Formation of a uniform thin film over a wide range is enabledby annular scanning (FIG. 8), linear scanning (FIG. 9), scanning indotted lines (FIG. 10) and scanning of a set of points (FIG. 11).

Generally, intensity distribution of laser is of gauss type or has a tophat shape. However, a desirable light intensity distribution may beformed in advance in the laser unit 10. FIG. 2 shows an example which iscalled an instable type resonator in which a partial reflection mirror4211 having a convex shape and a total reflection mirror 4212 having aconcave shape with a gain portion 4210 interposed constitute aresonator. In this example, the laser output will be annular, as shownin the figure. However, though the distribution is annular, thedirection of progress of the light is the same, and therefore whenfocused, the light is condensed to one point. Therefore, instead of acondenser lens, a lens unit forming images corresponding to the lightintensity distribution just out of the laser unit must be incorporated.

FIG. 13 shows an example in which a reflection mirror 4213 having anaperture is used as the partial reflection mirror of the laser unit. Ifthe light emitted from the laser unit is masked, the intercepted lightis lost. However, in this case, the intercepted light is returned to thegain portion 4210 to be amplified once again.

A second embodiment of the present invention and its modification willbe described with reference to FIGS. 14 and 19.

FIG. 14 is a schematic diagram of one example of the thin film formingapparatus using laser for implementing the present invention. In thethin film forming apparatus using laser shown in FIG. 14, laser beam 14generated from laser unit 10 has portions having weak beam intensity atthe periphery of the beam cross section cut by a laser beam shieldingplate 4804 and only the central portion is condensed by condenser lens 9and directed to target 5 placed in chamber 1. Chamber 1 can be evacuatedto a high vacuum.

A substrate 2 is placed opposing to target 5. Laser beam 16 evaporatestarget 5 and generates a plume 15. Plume 15 is a plasma includingparticles of the same composition as the target, and a thin film isdeposited on the contact surface between substrate 2 and plume 15.

The cross section of the excimer laser beam used in the method offorming thin film using laser generally has such an energy densitydistribution that is flat at the center and attenuated at the periphery.The target evaporated by the skirt of the beam cross section which isthe portion having small laser energy density results in drops havingthe diameter of about 1 μm, which drops grow in the plume and aredeposited on the substrate. Consequently, unevenness having the diameterof about 1 μm is generated on the substrate, degrading the film quality.In the method of the present invention, the laser beam is passed througha shielding plate which allows only the central portion of the laserbeam to pass therethrough, in order to reduce the scope of the intensitydistribution of the laser beam cross section, and the target isirradiated with this beam, evaporation of the target in the form ofdrops can be prevented.

FIG. 15A shows the manner of converting the beam cross section on thetarget 5 to a square by controlling incident angle of laser beam 16 withrespect to target 5. The incident angle θ of laser beam 16 with respectto target 5 is selected to satisfy a/b=sin θ, where a and b respectivelyrepresent lengths of shorter and longer sides of the shape of the beamin the vertical cross section with respect to the direction of progressof the laser beam as shown in FIG. 15B, and it is assumed that thelonger side will be incident on the surface of target 5 in parallel.Accordingly, laser beam 16 on the surface of target 5 is converted intoa square the side of which has the length of b.

Generally, the excimer laser has rectangular beam cross section, andtherefore the cross sectional shape of the plume generated on thesurface of the target irradiated with the laser beam also comes to havea rectangular shape. The initially generated plume having therectangular cross section has different density gradient of plasma inthe shorter side and the longer side. Accordingly, during the progressof the plume in the chamber to reach the substrate, the distribution ofactive particles constituting the plume in the cross section of theplume changes, degrading the film quality distribution of the depositedthin film. In the method of this embodiment, the incident angle of thelaser beam with respect to the target is controlled, and a cylindricallens is used so as to shape the laser beam cross section on the targetto a square, whereby the distribution of the active particle density inthe cross section of the generated plume can be made uniform.

FIG. 16A is a schematic diagram showing an example of an apparatus forchanging the shape of the cross section of laser beam 16 by using a beamshape converting element 4805. Laser beam 16 emitted from laser unit 10has its rectangular cross section 4806 shown in FIG. 16B changed to asquare beam cross section 4807 shown in FIG. 16C, the target 5 isirradiated with this beam, and plume 15 is generated.

FIG. 17 is a schematic diagram showing an example of an apparatus forchanging the cross section of the beam on target 5 to a square by usinga cylindrical lens 4809. Only the long side direction of the rectangularcross section of laser beam 16 is selectively condensed by cylindricallens 4809, and therefore when incident on target 5, the beam has itscross section converted to a square.

FIG. 18 is a schematic diagram showing an example of an apparatus forchanging the position of irradiation of target 5 with laser beam 16 byusing a movable condenser lens 4810. The movable condenser lens 4810 hasits set inclination and position changed at every pulse of laser beam16, so that the position of irradiation of target 5 with laser beam 16can be changed.

When only one point of the target is irradiated with a laser beam, onlya portion of the target is locally sputtered, and therefore a crater isgenerated, particle composition of the generated plume changes, and thefilm thickness distribution and the quality of the deposited thin filmvaries. In the method of the present invention, the lens for condensinglaser beam is made movable and the condenser lens is moved at everylaser pulse, and in addition, the partial reflection mirror of theoptical resonator in the laser unit is moved a little by every pulse soas to change the mode of the laser beam, whereby the position of laserbeam generation on the target can be changed.

FIG. 19 is a schematic diagram showing an example of an apparatus forchanging position of irradiation of target 5 with laser beam 16 bymaking movable the partial reflection mirror 4813 of the opticalresonator in laser unit 10. The movable partial reflection mirror 4813has its set inclination changed at every pulse of laser beam 16, so thatthe position of irradiation of target 5 with laser beam 16 can bechanged.

By using the apparatus of FIG. 14, a Y₁ Ba₂ Cu₃ O_(7-x) oxidesuperconductive thin film was fabricated in accordance with the methodof the present embodiment. An SrTiO₃ single crystal substrate was usedas the substrate 2, and the substrate temperature was 700° C. A sinteredbody of Y₁ Ba₂ Cu₃ O_(7-x) having the diameter of 2 cm was used astarget 5. The distance between substrate 2 and target 5 was 5 cm. Theinside of chamber 1 was evacuated to 1×10⁻⁴ Torr, and then oxygen gaswas introduced to 200 m Torr. A laser beam shielding plate having arectangular aperture at the center was placed between laser unit 10 andcondenser 9.

As excimer laser having the wavelength of 19 nm was used as the laser.The laser beam cross section of about 6×12 mm² had the peripheralportion cut by the beam shielding plate, resulting in the cross sectionof 4×10 mm².

The laser output was set to 3 J/cm², the area of laser beam irradiationwas 1×2.5 mm², and the pulse frequency was set to 2 Hz. The target wasrotated at 120 rpm.

Film formation was carried out for 40 minutes under the above describedconditions, and the film thickness distribution and superconductivecharacteristics of the obtained oxide superconductive thin film weremeasured, and the surface of the thin film was observed by scanningelectron microscope (SEM). Consequently, the variation in film thicknessdistribution in the oxide superconductive thin film fabricated inaccordance with the method of the present invention was ±5% in a circlehaving the diameter of 25 mm. By SEM observation, about 5 sphericalprotrusions having the diameter of about 1 μm were observed per 10×10μm² on the substrate surface. Meanwhile, the variation in film thicknessdistribution when the thin film was formed under the same conditionswith similar laser energy density but not using the beam shielding platewas ±10% in the circle having the diameter of 25 mm, and about 10spherical protrusions were observed per 10×10 μm² by SEM observation.The critical temperature of the oxide superconductive thin filmfabricated in accordance with the method of the present invention was87K and the average film thickness was about 3000 Å.

A Y₁ Ba₂ Cu₃ O_(7-x) oxide super conductive thin film was fabricated inaccordance with the method of the present embodiment by using theapparatus of FIG. 15A. An SrTiO₃ single crystal substrate was used assubstrate 2, and the temperature of the substrate was 700° C. A sinteredbody of Y₁ Ba₂ Cu₃ O_(7-x) having the diameter of 2 cm was used astarget 5. The distance between substrate 2 and target 5 was 5 cm. Theinside of chamber 1 was evacuated to 1×10-4 Torr, and then oxygen gaswas introduced to 200 m Torr.

An excimer laser having the wavelength of 193 nm was used as the laser.The cross section of the laser beam was about 6×12 mm², and the incidentangle θ of laser beam 16 with respect to target 5 was set to 30° C. Thelaser output was set to 3 J/cm², the area of laser beam irradiation was2×2 mm², and the pulse frequency was 2 Hz. The target was rotated at 120rpm.

Film formation was carried out for 25 minutes under the above describedconditions, and film thickness distribution and superconductivecharacteristics of the obtained oxide superconductive thin film weremeasured. Consequently, the variation of film thickness distribution ofthe oxide superconductive thin film fabricated in accordance with themethod of the present invention was ±5% in a circle having the diameterof 25 nm. The critical temperature was 93K. The variation in the filmthickness distribution of the film formed under the same conditionsexcept that the incident angle of the laser beam was 60° C. was ±10% inthe circle having the diameter of 25 nm, and the critical temperaturewas 87K. The average film thickness of the oxide superconductive thinfilm fabricated in accordance with the method of the present inventionwas about 300 Å.

A Y₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thin film was formed inaccordance with the method of the present embodiment using the apparatusof FIGS. 16 and 17. An SrTiO₃ single crystal substrate was used assubstrate 2, and the temperature of the substrate was 700° C. A sinteredbody of Y₁ Ba₂ Cu₃ O_(7-x) having the diameter of 2 cm was used astarget 5. The distance between substrate 2 and target 5 as 5 cm. Theinside of chamber 1 was evacuated to 1×10⁻⁴ Torr, and then oxygen gaswas introduced to 200 m Torr. A cylindrical lens 4809 was placed betweenlaser unit 10 and condenser lens 9.

An excimer laser having the wavelength of 193 nm was used as the laser.The cross section of the laser beam was about 6×12 mm², the laser outputwas set to 3 J/cm², the area of laser beam irradiation was 2×2 mm², andpulse frequency was set to 2 Hz. The target was rotated at 120 rpm.

Film formation was carried out for 25 minutes, and film thicknessdistribution and the superconductive characteristics of the obtainedoxide superconductive thin film were measured. Consequently, thevariation in film thickness distribution of the superconductive thinfilm fabricated in accordance with the method of the present inventionwas ±5% in a circle having the diameter of 25 mm. The criticaltemperature was 93K. The variation in film thickness distribution of afilm formed under the same conditions but not using cylindrical lens4809 was ±10% in the circle having the diameter of 25 mm, and thecritical temperature was 87K. The average film thickness of the oxidesuperconductive thin film fabricated in accordance with the method ofthe present invention was about 3000 Å.

A Y₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thin film was formed inaccordance with the method of the present embodiment by using theapparatus of FIG. 18. An SrTiO₃ single crystal substrate was used assubstrate 2, and temperature of the substrate was set to 700° C. Asintered body of Y₁ Ba₂ Cu₃ O_(7-x) having the diameter of 2 cm was usedas target 5. The distance between substrate 2 and target 5 was set to 5cm. The inside of chamber 1 was evacuated to 1×10⁻⁴ Torr, and thenoxygen gas was introduced to 200 m Torr. Film formation was carried outwhile movable condenser lens 4810 was moved slightly at every laserpulse.

An excimer laser having the wavelength of 193 nm was used as the laser.The laser beam cross section was about 6×12 mm², the laser output wasset to 3 J/cm², the area of laser beam irradiation was 1×2 mm² and thepulse frequency was 2 Hz. The target was rotated at 120 rpm.

Film formation was carried out for 50 minutes, and the film thicknessdistribution and the superconductive characteristics of the obtainedoxide superconductive thin film were measured. As a result, variation inthe film thickness distribution of the oxide superconductive thin filmformed in accordance with the method of the present invention was ±10%in a circle having the diameter of 25 mm. The critical temperature was93K. The variation in film thickness distribution of a film formed underthe same conditions as described above with the movable condenser lensfixed was ±10% in the circle having the diameter of 25 mm, and thecritical temperature was 87K.

The average film thickness of the oxide superconductive thin filmfabricated in accordance with the method of the present invention wasabout 3000 Å.

A Y₁ Ba₂ Cu₃ O_(7-x) superconductive thin film was fabricated inaccordance with the method of the present embodiment by using theapparatus of FIG. 19. An SrTiO₃ single crystal substrate was used assubstrate 2, and the substrate temperature was 700° C. A sintered bodyof Y₁ Ba₂ Cu₃ O_(7-x) was used as the target. The distance betweensubstrate 2 and target 5 was 5 cm. The inside of chamber 1 was evacuatedto 1×10⁻⁴ Torr, and then oxygen gas was introduced to 200 m Torr. Thefilm was formed with the movable partial reflection mirror 4813 movedslightly at every laser pulse.

An excimer laser having the wavelength of 193 nm was used as the laser.The laser beam cross section was about 6×12 mm², the laser output wasset to 3 J/cm², the area of laser beam irradiation was 1×2 mm², and thepulse frequency was 2 Hz. The target was rotated at 120 rpm.

Film formation was carried out for 50 minutes under the above describedconditions, and the film thickness distribution and the superconductivecharacteristics of the obtained oxide superconductive thin film weremeasured. As a result, the variation in film thickness distribution ofthe oxide superconductive thin film fabricated in accordance with themethod of the present invention was ±10% in a circle having the diameterof 25 mm. The critical temperature was 93K. The variation in filmthickness distribution of a film formed under the same conditions exceptthat the movable partial reflection mirror was fixed was ±10% in thecircle having the diameter of 25 mm, and the critical temperature was87K. The average film thickness of the oxide superconductive thin filmfabricated in accordance with the method of the present invention wasabout 3000 Å.

A third embodiment of the present invention will be described. FIG. 20shows a structure of a film forming apparatus in accordance with thethird embodiment of the present invention. Referring to FIG. 20, theapparatus of this embodiment includes a laser oscillator 10, a polygonmirror 8 for laser scanning, a target 5 and a substrate 2.

The functions of various portions of the apparatus shown in FIG. 20 areas follows. The beam emitted from the laser oscillator was condensed bya condenser lens to be incident on the target. Consequently, a plume isgenerated on the target, and the substances included in the plume aredeposited on the substrate to form a thin film. Here, the area on whichthe film can be formed by one plume is limited. In order to form a filmover wider area, a rotatable polygon mirror for laser beam scanning isinserted in the optical path of the laser beam so as to change thedirection of the laser beam, whereby the position of plume generation onthe target is moved, enabling film formation on wider area.Consequently, by such a simple mechanism as to rotate a polygon mirroronly, a uniform thin film can be formed over a wide area.

A fourth embodiment of the present invention will be described. FIG. 21is a schematic diagram showing a structure of the film forming apparatusin accordance with the fourth embodiment of the present invention.Referring to FIG. 21, the apparatus of this embodiment includes a laseroscillator 10, a mirror 8 for guiding the laser beam to the target, anacoustic optical element 18, a target 5 and a substrate 2.

The functions of various portions of the apparatus shown in FIG. 21 areas follows. The light beam emitted from the laser oscillator iscondensed by a condenser lens to be incident on the target.Consequently, a plume is generated on the target, and substancesincluded in the plume are deposited on the substrate to form a thinfilm. Here, the area on which film can be formed by one plume islimited. In order to form a film over a wide area, an acoustic opticalelement controlling the direction of progress of the light beam by sonicdeflection is inserted in the optical path of the laser beam, so as tochange the direction of the laser beam. Thus the position of plumegeneration on the target is moved, enabling film formation over a widerarea. Consequently, without any complicated mechanism for moving theoptical element, a uniform thin film can be formed over a wide area.

A fifth embodiment of the present invention will be described. FIG. 22is a schematic diagram showing the structure of the film formingapparatus in accordance with the fifth embodiment of the presentinvention. Referring to FIG. 22, the apparatus of the present embodimentincludes a laser oscillator 10, a mirror 19 constituting a resonator ofthe laser oscillator, a mirror 8 for guiding the laser beam to thetarget, a target 5 and a substrate 2.

The functions of various portions of the apparatus shown in FIG. 22 areas follows. The beam emitted from the laser oscillator is incident onthe target. Consequently, a plume is generated on the target, and thesubstances included in the plume are deposited on the substrate to forma thin film.

Here, the area on which the film can be formed by one plume is limited.In order to form a film over a wider area, the direction of laser beamemission from the laser oscillator is changed by moving the resonatormirror of the laser oscillator, so that the position of plume generationon the target is moved, enabling film formation over a wide range.Consequently, without inserting any special optical element for laserbeam scanning, a uniform thin film can be formed over a wide area.

A sixth embodiment of the present invention will be described. FIG. 23is a schematic diagram showing the structure of the film formingapparatus in accordance with this embodiment of the present invention.Referring to FIG. 23, the apparatus of the present embodiment includes alaser oscillator 10, a divided type adaptive mirror 25, a target 5 and asubstrate 2.

Functions of the various portions of the apparatus shown in FIG. 23 areas follows. The beam emitted from the laser oscillator is condensed bythe divided type adaptive mirror to be incident on the target.Consequently, a plume is generated on the target, and substancesincluded in the plume are deposited on the substrate to form a thinfilm. Here, the area on which the film can be formed by one plume islimited. In order to form a film over a wide area, a divided typeadaptive mirror including a number of minute mirrors collectivelyserving as one mirror with the angle and position of each can beprecisely controlled, such as shown in FIGS. 24A and 24B, is used. Bychanging the curvature and angle of the mirror as a whole by controllingeach minute mirror, the point of focus of the laser beam is moved on thetarget so as to change the position of plume generation on the target,enabling film formation over a wide area. Consequently, since laserirradiation point having similar condensed pattern can be formedconstantly at any position on the target, plumes having uniform naturecan be generated at any position of the target, and therefore a uniformthin film can be formed over a wide area.

A seventh embodiment of the present invention will be described. FIG. 25is a schematic diagram showing a structure of the film forming apparatusin accordance with this embodiment of the present invention. Referringto FIG. 25, the apparatus of this embodiment includes a laser oscillator10, a lens 21 for directing the laser beam to an optical fiber, anoptical fiber 22, a target 5 and a substrate 2.

Functions of various portions of the apparatus shown in FIG. 25 are asfollows. The beam emitted from the laser oscillator is guided near thetarget by using the optical fiber to be incident on the target.Consequently, a plume is generated on the target, and the substancesincluded in the plume are deposited on the substrate to form a thinfilm.

Here, the area on which the thin film can be formed by one plume islimited. In order to form a film over a wide area, the laser beamemitting point of the optical fiber is moved near the target as shown inthe figure so that the target is scanned with the point of focus of thelaser beam. Consequently, the position of plume generation is changed onthe target, enabling film formation over a wide range. Consequently, thelaser beam irradiation point having similar pattern can be formedconstantly at any position on the target, a plume having uniform naturecan be generated at any position on the target, and therefore a uniformthin film can be formed over a wide area.

An eighth embodiment of the present invention will be described withreference to FIG. 26. Referring to FIG. 26, parallel laser beams 16generated from laser unit 10 has the direction of the beams changed whenthey passed through laser beam deflection means 511. The laser beam arecondensed by-condenser lens 9 to be incident on the raw material targetplaced on a turntable 11 in the chamber 1.

At this time, since the direction is changed by deflection means 551,different portions of raw material target 5 are sputtered to generateplumes 15. A substrate 2 is placed fixed on a substrate holder 3opposing to raw material target 5, and excited atoms and ions in theplumes 15 reach the substrate 2 and are deposited thereon, forming athin film.

The operation will be described. By using laser beam deflection mean551, it becomes possible to generate plumes from the entire area of thetarget, and when a target having the same or larger area than the waferis used, a uniform thin film can be formed over a wide area.

As for the deflection means, a mirror which rotates or vibrates insynchronization with the laser pulse may be used. An electro-opticaldeflector, or an acoustic optical deflector such as disclosed in OpticalWave Electronics, CORONA Publishing Co., Ltd. pp. 278-286 may be used toobtain the similar effect. Further, since these deflectors do not haveany movable portions, they are highly reliable, and they allow highspeed operation. A hologram scanner may be used as the deflection means.

Focal length of the condenser lens is long, and therefore the sizes ofthe laser beams focused on the entire surface of the target areapproximately the same. However, when a lens having shorter focal lengthis used, the shape of the laser beam varies, which prevents formation ofa uniform thin film, as the energy density of the laser beam varies. Inthat case, a condenser lens of which focal length can be changed insynchronization with the deflection means may be used to enableformation of a uniform thin film.

As for the condenser lens having variable focal length, an elementformed by a liquid crystal having the shape of a lens with electrodesprovided may be used. In such an element, refractive index changes dueto the electro-optical effect of the liquid crystal when a voltage isapplied to the electrodes, so that the focal length of the lens changes.By applying a voltage in synchronization with the deflection means tochange the focal length, the entire area of the target can be irradiatedwith the laser beam having the same energy density.

A deflection condenser element having the function of both deflectingmeans 551 and condenser lens 9 may be used. As such deflection condenserelement, an element including a number of holograms having differentdirections of deflection and different focal lens arranged in the shapeof a rotatable disk, may be used. Various spatial optical modulator maybe used to provide the similar effect.

A ninth embodiment of the present invention will be described. FIG. 27is a schematic diagram showing the structure of the film formingapparatus in accordance with this embodiment of the present invention.Referring to FIG. 27, the apparatus of this embodiment includes laseroscillator 10, a condenser lens 9, a laser scanning mirror 8, a target5, a substrate 2 and a control apparatus 13.

Functions of various portions of the apparatus shown in FIG. 27 are asfollows.

The beam emitted from the laser oscillator is condensed by a condenserlens to be incident on the target. Consequently, a plume is generated onthe target, and the substances included in the plume are deposited onthe substrate to form a thin film. Here, the area on which the film canbe formed by one plume is limited. In order to form a film over widearea, a laser scanning mirror is inserted in the optical path of thelaser beam so as to move the position of plume generation on the target,enabling film formation over a wide range. However, at the time of laserbeam scanning, the optical path length from the condenser lens to thetarget changes. Consequently, the condensed pattern of the beam on thetarget changes, causing change in the nature of the generated plume.This prevents formation of a uniform film. Therefore, in relation to thelaser beam scanning, the position of the condenser lens is controlled sothat the optical path length from the condenser lens to the target iskept constant. Consequently, even if laser beam scanning is carried out,the nature of the plume generated can be kept constant, so that auniform thin film can be formed over a wide range.

A tenth embodiment of the present invention will be described. FIG. 28is a schematic diagram showing the structure of the film formingapparatus in accordance with this embodiment of the invention. In thisembodiment, the focal length of the condenser lens 9 is set to 600 mm.

The functions of various portions of the apparatus shown in FIG. 28 areas follows. The beam emitted from the laser oscillator is condensed bythe condenser lens to be incident on the target. Consequently, a plumeis generated on the target, and the substances included in the plume aredeposited on the substrate, forming a thin film. Here, the area on whicha film can be formed by one plume is limited. In order to form a filmover a wide area, a mirror for laser beam scanning is inserted in theoptical path of the laser beam so as to move the position of plumegeneration on the target, enabling film formation over a wide area.However, at the time of laser beam scanning, the optical path lengthfrom the condenser lens to the target changes, so that the condensedpattern of the beam on the target changes, causing change in the natureof the generated plume. This prevents formation of a uniform film.During the laser beam scanning, the optical path length changes at leastby ##EQU1## where d represents the width of the substrate and frepresents the focal length of the condenser lens, as shown in FIG. 29.When the beam diameter is measured near the point of focus when anexcimer laser beam having the beam diameter of 10 mm is incident on thelens having the focal length of 600 mm, the diameter is 0.58 mm at thepoint of focus, while the beam diameter is changed to 0.62 mm at aposition shifted by the above described amount of change in the opticalpath length. The change in the beam diameter is within 10% when a lenshaving the focal length of 600 mm is used, and therefore the change inthe nature of the plume is not significant. Therefore, by setting thefocal length of the condenser lens to be at least 600 mm, the nature ofthe plume generated can be kept constant even when laser beam scanningis carried out, and therefore uniform thin film can be formed over awide range.

An eleventh embodiment of the present invention will be described. FIG.30 is a schematic diagram showing the structure of the film formingapparatus in accordance with this embodiment. Referring to FIG. 30, inthis embodiment, the beam emitted from the laser oscillator is condensedby a condenser lens to be incident on the target. Consequently, a plumeis generated on the target and the substances included in the plume aredeposited on the substrate to form a thin film. Here, the area on whicha film can be formed by one plume is limited. In order to form a filmover a wide range, a method is known in which a mirror for laser beamscanning is inserted to the optical path of the laser beam to change thedirection of the laser beam, so that the position of plume generation ismoved on the target, enabling film formation over a wide area. However,at the time of laser beam scanning, the optical path length from thecondenser lens to the target changes, causing change in the condensedpattern of the beam on the target. Consequently, the nature of thegenerated plume is changed, preventing formation of a uniform film.Therefore, in laser beam scanning, the mirror guiding the laser beam tothe target and the condenser lens are moved parallel to the substrate soas to scan the plume generating points on the target without changingthe distance between the condenser lens to the target. Consequently,even when plume generation points are scanned, the nature of the plumesgenerated are kept constant, so that a uniform thin film can be formedover a wide area.

A twelfth embodiment of the present invention will be described withreference to FIGS. 31A and 31B. Referring to FIGS. 31A and 31B, theapparatus of this embodiment includes a mirror 112 for directing thelaser beam 16 to the raw material target 15, a mirror 113 havingdifferent angle of reflection from mirror 112, and a rotation axis 114for rotating mirrors 112 and 113.

The operation will be described. The process of film formation is thesame as in the prior art. In the prior art, laser beam 16 is incident onone point of target 15. In this invention, the laser beam 16 can bedirected to different positions of target 5 alternately by mirrors 112and 113. First, laser beam 16 impinges on the target 5 by means of themirror 112 so as to generate plume 115, and a thin film is formed on thesubstrate. Then, the mirrors are rotated by rotation axis 114 and thelaser beam 16 is reflected by mirror 113, whereby a plume 116 isgenerated at a position different from that of plume 115 (FIG. 31B). Thethin film formed on the substrate 2 is formed at a position of thesubstrate where the plume reaches. In the prior art, thin film is formedby only one plume. In this embodiment, thin film is formed by twoplumes. Therefore, compared with the prior art, the thin film can beformed over wider area in the present invention. Though two mirrors areemployed in this embodiment, three or more mirrors may be used, and thelarger the number of mirrors, the wider becomes the area of thin filmformation.

A thirteenth embodiment of the present invention will be described withreference to FIGS. 32, 33A and 33B.

The main feature of the embodiment resides in that when a film is to beformed with the portion where the thin film is mainly deposited on thesubstrate is changed by moving the position of the substrate in the filmforming chamber, the speed of movement of the substrate is selected sothat the point of contact of the substrate and the central axis of theplume do not overlap any such point of contact in the previous periods,with the movement takes place in one period. Above a position of thetarget which is irradiated with the laser beam, there is generated aplasma which is a collection of active film forming particles called aplume, and the most efficient reaction occurs near the tip end thereof.In the method of forming a thin film using laser, generally thesubstrate is moved so that a thin film is deposited over a wide area, sothat the position of the substrate which is brought into contact withthe plume is changed for thin film deposition. In the method of thepresent invention, the speed of movement of the substrate is selectedsuch that the intersection with the substrate and the central axis ofthe plume differs from the point of contact of the preceding periods inthe movement of one period.

In a method of forming thin film using laser in which thin film isdeposited with the substrate moved, about 30 minutes are necessary toform a film as thick as about 3000 Å. During this period, if the periodof the pulse of the laser and the speed of rotation of the substrate arein synchronization, film is formed concentrated on the a specificportion of the substrate, resulting in uneven film thicknessdistribution. In the method of the present invention, in a period ofmovement of the substrate, the speed of movement of the substrate isselected in accordance with the frequency of the laser pulse such thatthe point of contact between the substrate and the central axis of theplume differs from the point of contact in the preceding movement of thesubstrate, and therefore a thin film having uniform film thicknessdistribution can be deposited over a wide area. This embodiment will bedescribed in greater detail in the following.

FIG. 32 shows an example of the thin film forming apparatus using lasercarrying out the present embodiment. In the thin film forming apparatususing laser shown in FIG. 32, laser beam 16 emitted from laser unit 10and passed through condenser lens 9 enters an inlet window 7 of chamber1 to be incident on target 5 which is placed on a turntable 11 inchamber 1. Turntable 11 can be rotated at an arbitrary rate of rotationby means of a motor 14. The inside of the chamber 1 can be evacuated toa high vacuum. A substrate 2 is placed opposing to target 5. In theapparatus of this embodiment, laser unit 10 oscillates the pulse laserbeam. When a thin film is to be deposited, substrate 2 rotates at anarbitrary rate by means of a motor 4801. The rate of rotation is set bya control apparatus 13 in accordance with the pulse frequency of thelaser beam such that the point of contact with the substrate 2 and theplume 15 at one rotation of the substrate differs from the point ofcontact of preceding periods, as shown in FIGS. 33A and 33B. FIGS. 33Aand 33B show loci of the points of contact between the central axis ofplume 15 and the surface of substrate 2. In each of the figures, pointof contact 4802 and point of contact 4803 are loci of contacts indifferent periods.

By using the thin film forming apparatus using laser described above, aY₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thin film was fabricated inaccordance with this embodiment. An SrTiO₃ single crystal substrate wasused as substrate 2, and the substrate temperature was set to 700° C. Asintered body of Y₁ Ba₂ Cu₃ O_(7-x) having the diameter of 2 cm was usedas target 5. The distance between substrate 2 and the target 5 was setto 5 cm. The inside of chamber 1 was evacuated to 1×10⁻⁴ Torr, and thenoxygen gas was introduced to 200 m Torr.

An excimer laser having the wavelength of 193 nm was used as the laser,the laser output was set to 3 J/cm², the area of laser beam irradiationwas 2×3.5 mm², and the pulse frequency was 2 Hz. The target was rotatedat 120 rpm.

Film formation was carried out for 25 minutes, and the film thicknessdistribution and the superconductive characteristics of the obtainedoxide superconductive thin film were measured. As a result, thevariation in film thickness distribution of the oxide superconductivethin film fabricated in accordance with the method of the presentinvention was ±5% in a circle having the diameter of 30 mm. Thevariation in film thickness distribution of a film formed under the samecondition except that the speed of rotation of the substrate wassynchronized with the frequency of the pulse laser was ±10% within thecircle having the diameter of 30 mm. The critical temperature of theoxide superconductive thin film fabricated in accordance with the methodof the present invention was 87K, and the average film thickness wasabout 3000 Å.

The substrate 2 in FIG. 32 can be scanned by using an XY stage providedin place of the motor 4801. In this case, also, the speed of scanning isselected such that the point of contact of the plume 15 and thesubstrate 2 differs from the point of contact in the preceding periods.

The variation in film thickness distribution of an oxide superconductivethin film formed by deposition under the same condition as describedabove by using a XY stage for scanning was ±5% within the area of 30×30mm². The variation in the film thickness distribution of a film formedunder the same condition except that the speed of scanning of thesubstrate was synchronized with the frequency of the pulse laser was±10% within the area of 30×30 mm², the critical temperature of the oxidesuperconductive thin film fabricated in accordance with the method ofthe present invention was 87K, and the average film thickness was about3000 Å.

A fourteenth embodiment of the present invention will be described. FIG.34 is a schematic diagram showing a structure of a film formingapparatus in accordance with the embodiment of the present invention.Referring to FIG. 34, in this embodiment, the beam emitted from thelaser oscillator is condensed by the condenser lens to be incident onthe target. Accordingly, a plume is generated on the target, and thesubstances included in the plume are deposited on the substrate to forma thin film. Here, the area and thickness of a film which can be formedby one plume are limited. Therefore, in order to form a film over a widearea with sufficient thickness, the laser beam is emitted repeatedly ina prescribed period, so that compositions of the thin film aresuccessively deposited on the substrate. At this time, if the intervalbetween the pulses is too short, new substances are deposited by thesucceeding pulse before the substances deposited by the preceding pulseare crystallized, preventing formation of a uniform film. Generally,since it takes about 1 second for the crystal to grow. Therefore, whenthe laser pulses are repeated at 1 Hz, the substances deposited by thepreceding pulse are crystallized sufficiently, and a uniform thin filmcan be generated.

A fifteenth embodiment of the present invention will be described. FIG.35 is a schematic diagram showing the structure of the film formingapparatus in accordance with this embodiment of the present invention.In this embodiment, a path scanning the point of irradiation circulatesonce in one second and returns to the original position.

Function of various portions of the apparatus shown in FIG. 35 are asfollows. The beam emitted from the laser oscillator is condensed by thecondenser lens to be incident on the target. Consequently, a plume isgenerated on the target, and the substances included in the plume aredeposited on the substrate to form a thin film. Here, the area andthickness of the film which can be formed by one plume are limited, andtherefore in order to form a film over a wide area with sufficientthickness, the position of plume generation is moved on the target so asto enable formation of the film over a wide area. At this time, if theperiod of scanning is too short, new substances are deposited by thesucceeding pulse before the substances deposited by the preceding pulseare crystallized, when the plume is generated again at the originalposition after one period of scanning. This prevents formation of auniform film. Generally, it takes about 1 second for the crystal togrow. Therefore, when scanning is carried out with the period of atleast 1 second, the substances deposited by the preceding pulse aresufficiently crystallized, enabling generation of a uniform thin film.

A sixteenth embodiment of the present invention will be described. FIG.36 is a schematic diagram showing a structure of the film formingapparatus in accordance with the embodiment of the present invention.Referring to FIG. 36, the apparatus includes a laser oscillator 10, acondenser lens 9, a mirror for laser scanning 8, a target 5, a substrate2 and a control apparatus 13. 15a denotes a newly generated plume, and15b denotes a plume which has been generated within the last 1 second.

Functions of various portions of the apparatus shown in FIG. 36 are asfollows. The beam emitted rom the laser oscillator is condensed by thecondenser lens to be incident on the target. Consequently, a plume isgenerated on the target, and substances included in the plume aredeposited on the substrate forming a thin film.

Now, the area and the thickness of a film which can be formed by oneplume is limited. Therefore, in order to form a film over a wide areawith sufficient film thickness, the position of plume generation ismoved on the target, enabling film formation over a wide area. At thistime, when the newly generated plume is overlapped with the plumegenerated immediately before, substances are newly deposited by thesucceeding pulse before the substance deposited by the preceding pulseare crystallized, which prevents formation of a uniform film. Generally,since it takes about 1 second for a crystal to grow, when the point ofplume generation is moved to such a point that the plume generated onthe target is not overlapped with the plume which has been generatedwithin last 1 second, the substances deposited by the preceding pulsecan be crystallized sufficiently, allowing generation of a uniform thinfilm.

A seventeenth embodiment of the present invention will be described withreference to FIG. 37. Referring to FIG. 37, in this embodiment, asubstrate 2 is placed at an opening of a raw material target 108 whichhas a cylindrical shape. Substrate 2 is heated by a heater 4. The laserbeam 16 emitted from laser unit 10 is condensed by condenser lens 9. Bycontinuously changing the relative angle between mirror 8 and laser beam16, inner circumference of the raw material target 108 is irradiatedthrough an inlet window 7. At the portion of the raw material target 108which is irradiated with laser, plasma is generated abruptly forming aplume 15. At this time, the plumes are generated continuously on theinner periphery of the raw material target 108. Consequently, thedistribution of the thin film on the substrate 2 is improved, allowingformation of the film over a wide area. Substrate 2 may be placed oneither side of the opening of the target 8, and substrates may be placedon both sides.

An eighteenth embodiment of the present invention will be described withreference to FIG. 38. Referring to FIG. 38, in this embodiment, a rawmaterial target 109 having a conical shaped with one portion cut away isplaced such that the surface thereof faces the substrate 2. Substrate 2is heated by heater 4. The laser beam 16 emitted from laser 10 iscondensed by condenser lens 9. By continuously changing the relativeangle between mirror 8 and laser beam 16, the circumferential surface ofraw material target 109 is irradiated through inlet window 7. At theportion of raw material target 109 irradiated with the laser, a plasmais generated abruptly, forming a plume. At this time, plumes 15 arecontinuously generated on the circumference of raw material target 109.Therefore, particles emitted to the space by the laser beam 16 fromentire circumferential directions of raw material target 109 reach thesubstrate 2 and are deposited thereon. Consequently, distribution of thethin film on the substrate 2 is improved, allowing formation of a thinfilm over a wide area. At this time, by changing the relative angle anddistance between substrate 2 and raw material target 109, thedistribution of the thin film deposited on the substrate 2 can bechanged.

A nineteenth embodiment of the present invention will be described withreference to FIG. 39. Referring to FIG. 39, the apparatus of the presentembodiment includes a laser unit 10, a lens 9 for condensing the laserbeam from laser unit 10 onto a target surface, a vacuum chamber 1, asubstrate 2, a substrate holder 3, a target 5 of a truncated conicalshape, an optical transmission window 7 having the shape of a dish or adoughnut, a rotary flat mirror 360, a mirror 361 having the truncatedconical shape and a rotary driving apparatus 362.

The operation will be described. The laser beam emitted from laser unit10 is condensed by lens 9 to be incident on a target 5 so thatsufficient optical density can be obtained. The laser beam transmittedthrough lens 9 is reflected by a rotary flat mirror 360 which is rotatedmaintained at a prescribed angle of inclination with respect to thelaser beam, by a rotary driving apparatus 362, and the beam is furtherreflected by the truncated conical mirror 361 placed opposing thereto,passes through the transmission window 7 at the upper portion of chamber1 to be incident on the target. By the high density laser beam incidenton the target, a plasma is generated abruptly. In the process of rapidcooling of the plasma, isolated excited atoms and ions are generated.These excited atoms and ions have the lives of several microseconds,generating a plume 15 which is like a flame. Meanwhile, a substrate 2 isplaced fixed on a substrate holder 3, opposing to the target 5. Theexcited atoms and ions in plume 15 reach the substrate 2, and aredeposited thereon to form a thin film.

The thickness of the thin film deposited on the surface of the substrate2 is distributed with the center being at the axis of the plume 15, andtherefore at this state, uniform film thickness cannot be obtained.

Here, the rotary flat mirror 360 is driven to rotate. Therefore the pathof the laser beam rotates and sweeps the concentrical circumference ofthe target 5, and the position of generation of the plume 15 moves inrotation on the target 5. Therefore, the point of contact between thecentral axis of plume 15 and the substrate 2 moves in rotation onsubstrate 2. Since the point of contact between the plume 15 and thesubstrate 2 is moved, the film thickness of the deposited film can bemade uniform, and thus a thin film having uniform thickness can beformed. Further, in order to cope with a substrate having large area, amechanism for automatically changing the angle of the rotary flat mirror360 may be provided, so that the portion of the laser beam incident onthe target 5 can be enlarged to a plane.

As shown in this embodiment, all driving mechanisms for sweeping thelaser beam are positioned outside of the vacuum chamber 1, so as tofacilitate maintenance thereof.

A twentieth embodiment of the present invention will be described withreference to FIGS. 40 to 42B.

Referring to FIG. 40, the apparatus of this embodiment includes a laserunit 10, a lens 9 for condensing laser beam from laser unit 10 to thesurface of a target, a vacuum chamber 1, a substrate 2, a substrateholder 3, a target 5, an optical transmission window 7, and a silentdischarge apparatus 363. FIGS. 41A, 41B and FIGS. 42A and 42B showdetails of the silent discharge apparatus, which apparatus includes adielectric cylinder 364 formed of quartz, ceramic or the like, anelectrode 365 in contact with the outer portion of the dielectriccylinder, a high frequency power source 366, an oxygen gas cylinder 367,a gas flow rate adjusting valve 368 and an orifice 369.

The operation will be described. The laser beam emitted from laser unit10 is condensed by lens 9 and focused on a target 5 so as to providenecessary light intensity. The laser beam passed through the lens 9passes through transmission window 7 of the chamber 1 to be incident ontarget 5. By the high density laser beam incident on the target, aplasma is generated abruptly, and during the process of cooling theplasma rapidly, isolated excited atoms and ions are generated. Theseexcited atoms and ions have the lives of several microseconds, forming aplume 15 which is like a flame. Meanwhile, a substrate 2 is placed fixedon a substrate holder 3, opposing to target 5. Excited atoms and ions inplume 15 reach the substrate 2, and are deposited thereon to form a thinfilm.

Meanwhile, the oxygen gas supplied from oxygen gas cylinder 367 is setto an arbitrary flow rate by gas flow rate adjusting valve 368, so thata prescribed amount of oxygen gas is introduced to silent dischargeapparatus 363. The side opposing to the gas inlet of the silentdischarge apparatus 363 is connected to chamber 1 by means of an orifice369, and by the function of orifice 369, the inside of silent dischargeapparatus 363 is kept at a pressure in the range from 0.1 to 50 Torr.Silent discharge apparatus 363 includes a dielectric cylinder 364 and apair of electrodes 365. A high voltage high frequency potential in therange of from 60 to 10 kHz is applied from high frequency power supply366, so that silent discharge occurs, and the supplied oxygen gas isexcited to oxygen ions and oxygen atoms. However, if the gas pressure isin the range of 0.1 to 50 Torr, the life of the oxygen ions is short, sothat most of the generated oxygen ions are eliminated, and the oxygenatoms are introduced to the chamber 3 through orifice 369 as the primarycomponent of the excitation seeds. The oxygen atoms introduced in thismanner oxidize the excited atoms and ions in plume 15 and, at the sametime, oxidize the elements constituting the thin film deposited on thesubstrate 2, so that an oxide thin film is formed.

In this case, the excitation seeds for oxidation are mainly oxygenatoms, so that accumulation of charges on the surface and impact of highspeed ions on the substrate surface can be avoided, and therefore thesubstrate is not damaged.

As for the structure of silent discharge apparatus 363, one electrode365 may be provided outside the dielectric cylinder 364 to apply a highvoltage high frequency potential, and the orifice 369 or chamber 1 maybe used as the ground electrode as shown in FIGS. 42A and 42B to obtainsimilar effect.

A twenty-first embodiment of the present invention will be describedwith reference to FIG. 43. Referring to FIG. 43, the apparatus of thisembodiment includes, on the side of a vacuum chamber 1, a pre-processingchamber 370, a substrate holder 371, a ultraviolet irradiating apparatus372 and a vacuum shut valve 373. Vacuum chamber 3 and pre-processingchamber 370 are connected with each other with the vacuum shut valve 373posed therebetween.

The operation will be described. The laser beam emitted from laser unit10 is condensed by dense 9 and focused on target 5 so that necessarylight intensity is obtained. The laser beam passes through lens 9 passesthrough the transmission window 7 of chamber 1 to be incident on target5. By the high density laser beam incident on the target 5, a plasma isgenerated abruptly, and in the process of cooling the plasma rapidly,isolated excited atoms and ions are generated. These excited atoms andions have lives of several microseconds, generating a plume 15 which islike a flame. Meanwhile, a substrate 2 is placed fixed on substrateholder 3, opposing to target 5. Excited atoms and ions in plume 15 reachthe substrate 2 and are deposited thereon, to form a thin film.

The substrate 2 used for forming the thin film is pre-processed in thefollowing manner. A substrate 4 subjected to etching for a short periodof time by using hydrofluoric acid is washed by water, dried, and thenplaced on a substrate holder 371 in pre-processing chamber 370. Then, itis subjected to radiation of ultraviolet ray by ultraviolet irradiatingapparatus 372 under vacuum. The substrate which has been subjected toultraviolet radiation is fed to vacuum chamber 1 through vacuum shutvalve 373.

The silicon substrate which has been pre-processed by hydrofluoric acidhas its natural oxide which has been formed on the surface thereofremoved, and because of the coupling between silicon atoms on thesubstrate surface and the fluorine in the processing solvent, thesurface becomes very stable, so that an oxide film is not easily formedeven if it is exposed to the atmosphere. However, since fluorine hasbeen coupled to the surface, proper characteristics of the thin filmcannot be obtained when a thin film is formed thereof. Therefore, it isnecessary to remove fluorine. Though fluorine which has been coupledwith silicon can be disconnected and removed when it is irradiated withultraviolet ray under vacuum, it is readily oxidized when it is exposedto oxygen. If the substrate can be conveyed under vacuum to a chamberfor thin film formation without exposing to the atmosphere, thin filmcan be formed on a clear surface.

A mercury lamp, a metal halide lamp or laser apparatus may be used asthe ultraviolet ray generating apparatus, provided that light having thewavelength in the range of ultraviolet ray can be obtained, to providesimilar effect.

Twenty-second embodiment of the present embodiment of the presentembodiment will be described with reference to FIG. 44. Referring toFIG. 44, the apparatus of this embodiment includes a half mirror 4001atransmitting 50% of laser beam 16, a mirror 4001b totally reflectinglaser beam 16, and lenses 9a and 9b for condensing laser beams 16a and16b.

The operation will be described. The laser beam 16 emitted from laserunit 10 is partially reflected by half mirror 4001a to be laser beam16a, while the remaining part is transmitted as it is. The transmittedlight is reflected by mirror 4001b to be laser beam 16b. The laser beamsare condensed on target 5 by corresponding lenses 9a and 9b.Consequently, two plumes 15a and 15b are generated parallel to eachother. Consequently, on substrate 2, thin films are formed in parallelat areas corresponding to these two plumes.

The effect of this beam division is proved from the following fact. Whenlaser beam 16 is condensed on the target 5 by lens 9, there is anoptimal value of the intensity of laser beam at the condense surface perunit area, as described, for example, in G. M. Davis and M. C. Gower,Appl. Phys. Lett., Vol. 55, No. 2, pp. 112-114 Jul. 10, 1989. Morespecifically, sputtering does not occur and thin film is not formeduntil the intensity exceeds a certain threshold value. However, if theintensity becomes too strong, sputtered substances in the form ofclusters are generated, and these substances are deposited as the thinfilm, which significantly degrades the quality of the thin film. Fromthis fact, it is impossible to increase the rate of sputtering byincreasing the laser beam intensity per unit area to increase the areaof thin film formation stepwise.

Meanwhile, forming a thin film over a wide area by increasing theintensity of laser beam 16 and enlarging the cross section of the beamso that the area of laser beam irradiation is enlarged while maintainingthe optimal laser intensity per unit area is impossible either, asdescribed in, for example, R. K. Singh et al., Physical Review B, Vol.41, No. 13, pp. 8843-8859 May 1, 1990.

In accordance with the description in this article, the higher thedensity of the generated plume becomes, the plume itself extends wider,and therefore even if the area of irradiation is enlarged to no purpose,it is apparent that a plume having larger cross section is notgenerated.

In view of these facts, in the present invention, a plurality ofirradiation spots are provided by dividing the beam into a plurality ofbeam, rather than enlarging the cross section of the laser beam 16, toform a thin film having superior quality over large area rapidly athighest efficiency.

Though the beam is divided into two in the description of thisembodiment, it is not limited thereto, and the beam may be divided intoplural beams.

Therefore, reflectance (or transmittance) of the mirror used is notlimited to the values of the embodiment above. When the nature orthickness of the thin film is to be controlled at various portions onthe substrate, reflectance (or transmittance) of each of the mirrors fordividing the beam into a plurality beams may be positively changed, soas to generate plumes corresponding to the desired nature or thickness.

A twenty-third embodiment of the present invention will be describedwith reference to FIG. 45. In this embodiment, referring to FIG. 45, thelaser beam 16 is enlarged to the size corresponding to a condensingsystem 4004 at a beam enlarging portion 4002, and enters the condensingsystem 4004 as an enlarged laser beam 4003. The condensing systemincludes a plurality of concave mirrors, and corresponding to respectiveconcave mirrors, laser beams 16a, 16b, 16c . . . are generated condensedby respective concave mirrors, which beams are generated to be incidenton the target.

Though concave lenses are used for dividing the beam in this embodiment.A convex lens may be used, or concave and convex lenses may be usedcombined. Though division and condensing are both carried out by asingle system, the division and condensing of the laser beam may becarried out by separate systems.

FIG. 46 is a top view of the chamber of the thin film forming apparatusdescribed above. The same numeral denote the same or correspondingportions. This embodiment is essentially the same as the twenty secondembodiment described above. However, the divided beams are adapted toenter the chamber through separate windows. By this structure, the loadof the laser beam inlet window 7 is reduced.

In the twenty-second and the twenty-third embodiment, one laser beam isdivided. However, a plurality of laser units may be used so that aplurality of laser beams are emitted. However, as can be seen in thepresent embodiment, the advantage of the method using a laser beamdivided into a number of beams is that all the resulting laser beamschange commonly in accordance with the change of the characteristics ofthe laser beam. Therefore, as compared with a case in which a pluralityof laser units are used, the reliability as the thin film formingapparatus is higher. From another view point, when the conditions of thelaser beam are to be controlled in the step of forming a thin film, ithas an advantage that all the divided beams can be controlled under thesame condition.

A twenty-fourth embodiment of the present invention will be describedwith reference to FIG. 47. In this embodiment, referring to FIG. 47, apowder target 4817 accommodated in a powder target container 4821 isscattered in the space of the chamber 1 together with a buffer gas flowthrough a nozzle 4820 by means of an air blower pump. The laser beamemitted from laser unit 10 and passed through condenser lens 9 entersthe inlet window 7 of chamber 1 and evaporates the powder target 4817floating in the space of the chamber 1, generating a number of plumes15. A substrate 2 is placed in the chamber 1, so that at the plane ofcontact of plume 15 and substrate 2, thin film is deposited. The laserbeam transmitted through the atmosphere of the powder target 4817 isreturned to the atmosphere of the powder target 4817 by means of a lightconfinement mirror 4823, so that it can evaporate the powder target 4817efficiently. On the surface of light confinement mirror 4823, a buffergas blow is applied by the air blower pump 4825 through nozzle 4824 sothat the powder target 4817 is not deposited on the surface of themirror. After laser beam irradiation, the powder target 15 floating inthe chamber 1 are evacuated through an absorption opening 4818 rapidlyby means of a pump 4819 to the outside of the chamber 1.

By using the thin film forming apparatus using laser described above, aY₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thin film was fabricated inaccordance with the method of the present invention. An SrTiO₃ singlecrystal substrate was used as the substrate 2, and the substratetemperature was 700° C. A Y₁ Ba₂ Cu₃ O_(7-x) was used as the powdertarget 4817. The inside of chamber 1 was evacuated to 1×10⁻⁴ Torr, andthen oxygen gas was introduced as buffer gas to 200 m Torr. An excimerlaser having the wavelength of 193 nm was used as the laser, the laseroutput was set to 2 J/cm², and the pulse frequency was set to 2 Hz.

Under the above described conditions, film formation was carried out for30 minutes, and the thickness distribution and superconductivecharacteristics of the obtained oxide superconductive thin film weremeasured. As a result, the distribution of film thickness of the oxidesuperconductive thin film fabricated in accordance with the method ofthe present invention was ±10% in the range of 40×50 mm². The variationof the film thickness of a film formed under the same condition inaccordance with the conventional method was ±10% in the scope of 35×35mm². The critical temperature of the oxide superconductive thin filmfabricated in accordance with the method of the present invention was87K, and the average film thickness was about 2000 Å.

A twenty-fifth embodiment of the present invention will be describedwith reference to FIG. 48. In this embodiment, referring to FIG. 48,powder target 4817 placed on a dish 4826 is blown by a buffer gas flow4827 ejected from a nozzle 4820 and scattered in the space of chamber 1.Meanwhile, laser beam 16 emitted from laser unit 10 and passed throughcondenser lens 9 enters the inlet window 7 of the chamber 1, evaporatesthe powder target 4817 floating in the space of chamber 1, and a numberof plumes 15 are generated. A substrate 2 is placed in the chamber 1, sothat at the contact surface of plume 15 and substrate 2, a thin film isdeposited. The laser beam 16 transmitted through the atmosphere ofpowder target 4817 during laser beam irradiation is returned to theatmosphere of powder target 4817 by means of light confinement mirror4823, so that it can efficiently evaporate powder target 4817. On thesurface of light confinement mirror 4823, the buffer gas flow is blownby means of the air blower pump 4825 through nozzle 4824, so that thepowder target 4817 is not deposited on the surface of the mirror. Afterthe laser irradiation, the powder target 15 floating in the chamber 1 israpidly evacuated to the outside of the chamber 1 through an absorptionopening 4818 by means of a pump 4819.

By using the thin film forming apparatus using laser described above, aY₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thin film was fabricated inaccordance with the method of the present invention. An SrTiO₃ singlecrystal substrate was used as the substrate 2, and the substratetemperature was set to 700° C. Y₁ Ba₂ Cu₃ O_(7-x) was used as the powdertarget 4817. After the inside of chamber 1 was evacuated to 1×10⁻⁴ Torr,oxygen gas was introduced as the buffer gas to 200 m Torr. An excimerlaser having the wavelength of 193 nm was used as the laser, the laseroutput was set to 2 J/cm², and the pulse frequency was set to 2 Hz.

Film formation was carried out for 30 minutes under the above describedconditions, and the thickness distribution and the superconductivecharacteristics of the obtained oxide superconductive thin film weremeasured. Consequently, the variation in film thickness distribution ofthe oxide superconductive thin film fabricated in accordance with themethod of the present invention was ±10% in the scope of 40×50 mm². Thevariation of the film thickness distribution of a film formed under thesame condition in accordance with the conventional method was ±10% inthe scope of 35×35 mm². The critical temperature of the oxidesuperconductive thin film fabricated in accordance with the presentinvention was 87K, and the average film thickness was about 2000 Å.

A twenty-sixth embodiment of present invention will be described withreference to FIG. 49. Referring to FIG. 49, in this embodiment, thepowder target 4817 is, immediately after ejection into the chamber 1 bynozzle 4820, rapidly evacuated to the outside of chamber 1 by anabsorption opening 4818 provided at a position opposing the tip of thenozzle 4820. The powder target 4817 emitted to chamber 1 is irradiatedwith laser beam 16, so that plumes 15 are generated.

In this embodiment, by using the thin film forming apparatus using laserdescribed above, a Y₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thin filmwas fabricated. An SrTiO₃ single crystal substrate was used as thesubstrate 2, and the substrate temperature was set to 700° C. A Y₁ Ba₂Cu₃ O_(7-x) was used as the powder target 4817. After the inside ofchamber 1 was evacuated to 1×10⁻⁴ Torr, oxygen gas was introduced as thebuffer gas to 200 m Torr. An excimer laser of the wavelength of 193 nmwas used as the laser, the laser output was set to 2 J/cm², and thepulse frequency was set to 2 Hz.

Film formation was carried out for 30 minutes under the above describedconditions, and the film thickness distribution and the superconductivecharacteristics of the obtained oxide superconductive thin film weremeasured. As a result, the variation in the film thickness distributionof the oxide superconductive thin film fabricated in accordance with themethod of the present embodiment was ±10% in the scope of 40×40 mm². Thevariations of the film thickness distribution of a film formed under thesame condition in accordance with the conventional method was ±10% inthe scope of 35×35 mm². The crystal temperature of the oxidesuperconductive thin film fabricated in accordance with this embodimentwas 87K, and the average film thickness was about 2000 Å.

A twenty-seventh embodiment of the present invention will be describedwith reference to FIG. 50. In this embodiment, referring to FIG. 50,substrates 2 are placed to surround the atmosphere of the powder target4817 floating in the space of chamber 1.

In this embodiment also, by using the thin film forming apparatus usinglaser, a Y₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thin film wasfabricated. An SrTiO₃ single crystal substrate was used as the substrate2, and 12 substrates were placed to surround the powder target 4817. Thesubstrate temperature was set to 700° C. Y₁ Ba₂ Cu₃ O_(7-x) was used aspowder target 4817. After the inside of chamber 1 was evacuated to1×10⁻⁴ Torr, oxygen gas was introduced as buffer gas, to 200 m Torr. Anexcimer laser having the wavelength of 193 nm was used as the laser, thelaser output was set to 2 J/cm², and pulse frequency was set to 2 Hz.

Film formation was carried out for 30 minutes under the above describedconditions, and film thickness distribution and the superconductivecharacteristics of the obtained oxide superconductive thin film weremeasured. As a result, 6 superconductive thin films were obtainedsimultaneously, with the variation in film thickness distribution being±10% in the scope of 35×35 mm², in accordance with the method of thepresent invention. When film is formed in the conventional method underthe same conditions, only one film could be obtained with the variationin distribution of film thickness being ±10% in the scope of 35×35 mm².The critical temperature of the oxide superconductive thin filmfabricated in accordance with the present invention was 87K, and theaverage film thickness was about 2000 Å.

A twenty-eighth embodiment of the present invention will be describedwith reference to FIG. 51. In this embodiment, referring to FIG. 51,laser beam 16 emitted from laser unit 10 and passed through condenserlens 9 enters the laser inlet window 7 of chamber 1, to be incident ontargets 5 placed on a pair of turntables 11 in chamber 1. Turntable 1can be rotated at an arbitrary rate by means of a motor 14. The insideof chamber 11 can be evacuated to high vacuum. The substrate 2 isarranged oblique to the normal of the surface of target 5. In order toenable radiation of a plurality of plume onto the substrate 2, aplurality of targets 5 are placed with respect to the substrate 2.

In this embodiment also, by using the thin film forming apparatus usinglaser described above, a Y₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thinfilm was fabricated. An SrTiO₃ single crystal substrate was used as thesubstrate 2, and the substrate temperature was set to 700° C. A sinteredbody of Y₁ Ba₂ Cu₃ O_(7-x) having the diameter of 2 cm was used as thetarget 5. The distance between the center of substrate 2 and the pointof irradiation of target 5 was set to 5 cm. After the inside of chamber1 was evacuated to 1×10⁻⁴ Torr, oxygen gas was introduced to 200 m Torr.

An excimer laser having the wavelength of 193 nm was used as the laser,the laser output was set to 3 J/cm², the area of laser irradiation was2×3.5 mm², and the pulse frequency was set to 2 Hz. The target wasrotated at 120 rpm.

Film formation was carried out under the above described conditions for25 minutes, and the film thickness distribution and the superconductivecharacteristics of the obtained oxide superconductive thin film weremeasured. Consequently, the variation in film thickness distribution ofthe oxide superconductive thin film fabricated in accordance with themethod of the present invention was ±10% in a circle having the diameterof 35 mm. The variation in film thickness distribution of a filmfabricated under the same conditions except that the substrate 2 isarranged so that the central axis of plume 15 and substrate 2 arevertical to each other and only one plume is used, was ±10% in a circlehaving the diameter of 10 mm. The critical temperature of the oxidesuperconductive thin film fabricated in accordance with the method ofthe present invention was 87K, and the average film thickness was about3000 Å.

A twenty-ninth embodiment of the present invention will be described.This embodiment is characterized in that a target having unevenness onthe surface which is to be irradiated with the laser beam is used in anapparatus for forming a thin film over a large area by using laser, inwhich a target is irradiated with laser beam and on a substrate placedopposing to the target, a thin film is deposited. The main feature ofthe embodiment resides in that a thin film is fabricated by using atarget having unevenness on its surface which is to be irradiated withlaser beam. In the film forming method using laser, generally, thetarget having flat surface is irradiated with a condensed laser beam, sothat the target is evaporated to generate a plasma, which is acollection of active film forming particles generally called a plume.Thin film is deposited by placing a substrate near the tip end of theplume. However, in that case, the thin film is formed only in a smallarea around a portion of the substrate which is in contact with the tipend of the plume. By the method of this invention, the target hasunevenness on its surface which is irradiated with laser beam, so that aplurality of plumes are generated from the protruding portions, allowingdeposition of a thin film over a wide area.

Further, in this embodiment, by making the height of the protrudingportions on the surface of the target increase successively from thedirection of laser beam irradiation, the target can be evaporatedefficiently to generate plumes.

FIG. 52 is a schematic diagram showing one example of the thin filmforming apparatus using laser, for carrying out the present invention.In the thin film forming apparatus using laser shown in FIG. 52, thelaser beam 16 emitted from laser unit 10 and passed through condenserlens 9 enters the laser inlet window 7 of the chamber 1 to be incidenton the raw material target 5 in chamber 1. The chamber 1 can beevacuated to high vacuum. Substrate 2 is placed to be opposing to thetarget 5. Target 5 has protruding portions of which height is graduallyincreased from the direction of the laser beam irradiation on itssurface.

In this embodiment also, by using the thin film forming apparatus usinglaser described above, a Y₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thinfilm was fabricated. An SrTiO₃ single crystal substrate was used as thesubstrate 2, and the substrate temperature was set to 700° C. A sinteredbody of Y₁ Ba₂ Cu₃ O_(7-x) was used as target 5. The distance betweenthe center of substrate 2 and the point of irradiation of target 5 wasset to 5 cm. After the inside of chamber 1 was evacuated to 1×10⁻⁴ Torr,oxygen gas was introduced to 200 m Torr. An excimer laser having thewavelength of 193 nm was used as the laser, the laser output was set to3 J/cm², the area of laser beam irradiation was 2×3.5 mm², and the pulsefrequency was set to 2 Hz.

Film formation was carried out under the above described conditions for25 minutes, and the film thickness distribution and the superconductivecharacteristics of the obtained oxide superconductive thin film weremeasured. Consequently, the variation in the film thickness distributionof the oxide superconductive thin film fabricated in accordance with themethod of the present invention was ±10% in the area of 40×50 mm². Thevariation in film thickness distribution of a film formed under the sameconditions except that a target having flat surface was used, was ±10%in a circle having the diameter of 30 mm. The critical temperature ofthe oxide superconductive thin film fabricated in accordance with thepresent invention was 87K, and the average film thickness was 3000 Å.

A thirtieth embodiment of the present invention will be described withreference to FIGS. 53A to 53C and FIG. 54. The basic structure of FIG.154 is the same as the prior art example shown in FIG. 149.

The operation will be described. The laser beam 16 emitted from laserunit 10 is transmitted through the laser inlet window 7 of chamber 1 butnot through condenser lens 9, to be nearly incident on raw materialtarget 5 placed on turntable 11 in chamber 11 or to be incident on awide range. The surface shape of the target may include half columns,triangular prisms, triangular pyramids, cones or hemispheres arrangedregularly or at random as shown in FIGS. 53A to 53C, and the shapes areadapted such that the incident angle of the excimer laser with respectto the target will be random, and therefore a plurality of plumes 15 andplasmas having very close width to that of plumes are generated verticalto the respective surfaces. In order to prevent sputtering of the sameportion, the target is supported by a rotary mechanism.

Opposing to the raw material target 5, substrate 2 is placed fixed onsubstrate holder 3. Excited atoms and ions in the plume 15 reachesubstrate 2 and are deposited thereon to form a thin film. Since aplurality of plumes are generated as described above, a thin film can beformed over a wide area relatively easily.

A thirty-first embodiment of the present invention will be describedwith reference to FIGS. 55 and 56. Referring to FIG. 55, the apparatusof this embodiment includes a beam splitter 300, a mirror 301, a linearmoving stage 302 and a linear moving stage controlling apparatus 303.

Portions denoted by the same reference numerals as in FIGS. 148 and 149denote the same or corresponding components.

The operation will be described. The laser beam emitted from laser unit10 is divided into a plurality of laser beam 16 by means of a pluralityof beam splitter 300, directions thereof are adjusted by a plurality ofmirror 301, and then the beams are condensed by a plurality of condenserlenses 9, passed through a plurality of laser inlet windows 7 of chamber1 to be incident on a plurality of portions of the raw material target 5placed on a turntable 11 in chamber 1. At this time, turntable 11 may berotated by a motor 14, so that sputtering of one portion only of the rawmaterial target 5 causing local generation of crater can be prevented.

At a plurality of portions of raw material target 5 irradiated withlaser beams, plasma of the target material is generated abruptly at thetime of laser irradiation. In the process of cooling the plasma inseveral ten ns, isolated atoms, molecules and ions are generated. Thegroups of excited atom molecules, ions and the like have lives of atleast several microseconds, which are emitted in the stage to generate aplurality of plumes 15 which are like flames of candles.

A substrate 2 is placed fixed on substrate holder 3 opposing to rawmaterial target 5. Excited atom molecules, ions and target material inthe form of clusters which are combinations of such atoms and ions inthe plurality of plumes 15 reach the substrate 2 and are deposited andcrystallized thereon, forming a thin film.

Here, linear moving stage 302 is controlled by linear moving stagecontrolling apparatus 303 and when raw material target 5 is linearlymoved in the direction of substrate 2, positions of irradiation on rawmaterial target 5 with a plurality of laser beams 16 are changed in theradial direction, and therefore the positions of a plurality of plumes15 generated on raw material target are changed in the radial direction.As a result, a plurality of plumes 15 are generated at various positionson substrate 2 placed opposite to raw material target 5. The targetmaterials in plume 15 reach and are deposited on various positions onthe surface of substrate 2. Accordingly, a uniform thin film having highquality can be formed on a large wafer having the diameter of 6 to 8inches or larger.

A heater 4 for heating the substrate is provided in substrate holder 3so as to enable post annealing in which a film deposited at a lowtemperature is annealed at a temperature higher than the temperature forcrystallization to obtain a thin film of high quality, and enablingas-deposition in which, at the time of deposition, the substrate itselfis held at a temperature higher than the temperature for crystallizationso that a crystallized thin film is formed at the site. In theas-deposition method, active oxygen atmosphere is utilized as well. Forexample, when an oxide thin film is to be formed as shown in the figure,a nozzle 6 for supplying gas 19 containing oxygen is provided so as toprovide oxygen atmosphere around the substrate 2 in order to promotegeneration of oxide on the substrate 2, as in the prior art.

In the embodiment, the laser beam is divided into a plurality of beamsby means of beam splitters. However, the laser beam may be divided intoa plurality of beams by using a total reflection mirror as shown in FIG.56 to obtain similar effect as in the example employing the beamsplitters. Compared with the beam splitters, when a total reflectionmirror is used, there is an advantage that the beam can be divided intoa plurality of beams with less attenuation of the laser beam intensity.

Though one laser beam is divided into a plurality of beams by means ofbeam splitters or a total reflection mirror in the above embodiment, aplurality of laser beams may be generated by using a plurality of laserunits to provide the same effect.

A thirty-second embodiment of the present invention will be describedwith reference to FIG. 57. The apparatus of this embodiment includes,referring to FIG. 57, a beam splitter 304, a mirror 305, a variableangle stage 306, and a variable angle stage controlling apparatus 307.

In the figure, portions denoted by the same reference characters as inFIGS. 148 and 149 denote the same or corresponding portions.

The operation will be described. The laser beam emitted from laser unit10 is divided into a plurality of laser beams 16 by means of a pluralityof beam splitters 304, and their directions are adjusted by a pluralityof mirrors 305. The beams are then condensed by a plurality of condenserlenses 9, and passed through a plurality of laser inlet windows 7 ofchamber 1 to be incident on a plurality of raw material targets 5 placedon a plurality of turntables 11 in chamber 1.

At this time, the plurality of turntables 11 may be rotated by means ofa plurality of motors 14 so as to prevent generation of local craterscaused by sputtering of the same portion of each of the plurality of rawmaterial targets 5.

At the portions of irradiation of the plurality of raw material targetswith laser, plasmas of the target material are generated abruptly at thetime of laser irradiation. In the process of cooling the plasma inseveral ten ns, isolated excited atom molecules, ions and the like aregenerated. These groups of excited atom molecules, ions and the likehave lives of at least several microseconds, and they are emitted in thespace to form a plurality of plumes 15 which are like flames of candles.

A substrate 2 is placed fixed on substrate holder 3 opposing to theplurality of raw material targets 5. The excited atom molecules and ionsas well as the target material in the form of clusters which are thecombination of these atoms and ions in the plurality of plumes 15 reachthe substrate 2 and are deposited and crystallized to form a thin film.

Here, the plurality of variable angle stages 306 are controlled byvariable angle stage controlling apparatus 307 and when, by thiscontrol, the angles of the plurality of raw material target 5 arechanged with respect to the substrate 2, the directions of the pluralityof plumes generated on the plurality of raw material targets 5 by theplurality of laser beams 16 are changed. Therefore, a plurality ofplumes 15 come to be in contact with various positions on the substrate2 placed opposing to the plurality of raw material targets 5.Accordingly the target material in the plume 15 reach and are depositedon various positions of the surface of substrate 2. Consequently, auniform thin film having high quality can be formed on a large waferhaving the diameter of 6 to 8 inches or larger.

A heater 4 for heating the substrate is provided in substrate holder 3so as to enable post annealing in which a film deposited at a lowtemperature is annealed at a temperature higher than the temperature forcrystallization to form a thin film of high quality and to enableas-deposition in which the substrate itself is held at a temperaturehigher than the temperature for crystallization at the time ofdeposition so as to form a crystallized thin film at the site. In theas-deposition method, an active oxygen atmosphere is utilized as welland, as shown in the figure, a nozzle 6 for supplying gas 19 containingoxygen is provided, for example, to provide oxygen atmosphere around thesubstrate 2, so as to promote generation of oxide on the substrate 2.

Though the laser beam is divided into a plurality of beams by means of abeam splitter in the present embodiment, the laser beam may be dividedinto a plurality of beams by using a total reflection mirror as shown inFIG. 56 to provide similar effect as in the example using the beamsplitters. As compared with the beam splitters, when a total reflectionmirror is used, there is an advantage that the beam can be divided intoa plurality of beams with less attenuation in the laser beam intensity.

Though one laser beam is divided into a plurality of beams by using beamsplitters or a total reflection mirror in the above describedembodiment, a plurality of laser beams may be generated by using aplurality of laser units to provide the same effect.

A thirty-third embodiment of the present invention will be describedwith reference to FIG. 58. Referring to FIG. 58, the apparatus of thisembodiment includes a CCD camera 241, a computer 242 for imagedistribution processing, an XY stage 243 for the laser, a support base244 and a computer 245 for controlling a mirror.

The operation will be described. When targets 5 are further rotated on arotating support base 244, plumes 15 having density distribution emittedfrom the targets are made uniform, enabling formation of a thin film ofhigh quality over a large area. At this time, by making the rotation ofthe motor and the operation of mirror synchronous with each other bymeans of computer 245 for controlling the mirror, the laser is adaptedto always be incident on the targets. Since there are a plurality oftargets at this time, the rate of deposition is increased. As the wafercan be scanned with the laser incident on the target moved by moving themirror and the reflected light is measured by the CCD camera, the stateof the film on the surface can be monitored on real time basis, theresult can be fedback to the film forming conditions so as to move thewafer or the targets, to change the shape of the beam, and to change theposition of the beam and so on.

A thirty-fourth embodiment of the present invention will be describedwith reference to FIGS. 59 to 67.

In this embodiment, referring to FIG. 59, when a target 5 is irradiatedwith a laser beam 16, compositions of target 5 are evaporated andscattered. When viewed as a whole, it seems like a flame of a candle,which is called a plume 15. When the plume is adjusted such that its tipend is in contact with the substrate 2, the compositions of the target 5are deposited on substrate 2 to form a thin film.

It is known that the direction of scattering of plume 15 from target 5is approximately the directions of the normal of the target. Since thetarget is generally a flat plate or a column having large diameter,plume 15 is mostly scattered in one direction. In that case, plume 15turns to be a thin flame, preventing formation of a thin film over awide area of the substrate. This problem can be solved when the targetis adapted such that there are a number of normals of the targetincluded in the scope which is irradiated with the laser beam. FIG. 59shows an example in which a columnar target is used. As shown by thearrows in the figure, there are a number of normals. Since plumes aregenerated in the direction of these normals, a large plume can begenerated when viewed as a whole.

FIGS. 60 and 61 show relation between the diameter D of the target andthe diameter ω of the laser beam 16. Referring to FIG. 60, assume thatlaser beam 16 is incident at the angle of θ₀ with respect to that one ofthe normals of the target 5 which is vertical to the substrate, theplume is generated to the annular direction which corresponds to thebeam diameter with θ₀ being the center. When the beam diameter ω issmall with respect to the diameter D of the target, such a plume asshown by the solid line 4220 shown in FIG. 61 will be generated.

Referring to FIG. 61, the plume extends in the angle of about ±πω/2D. Ifω/D is small, the plume is generated exclusively in the direction of θ₀.The plume is not generated to the direction of the substrate unless atleast the following relation is satisfied:

    πω/2D>θ.sub.0.

In order to satisfy this condition, the diameter of the laser beamshould be made larger with respect to the target, or the angle θ₀ shouldbe made smaller. The dotted line of FIG. 61 shows the intensitydistribution of the plume when the beam diameter is larger than thediameter of the target and the beam intensity distribution is uniform.This distribution results from the fact that the beam reaches the targetvertically as well as diagonally since the target is columnar in theexample of FIG. 60. When the beam reaches diagonally, the beam intensitybecomes weaker, so that the intensity of the plume is reducedaccordingly. In order to prevent this problem and to provide a flatplume, the intensity of the beam should be made larger as the anglecomes closer to 0 in FIG. 61.

Though a columnar target was used in the above example, the similareffect is expected even when a spherical or polygonal target is used,provided that a number of normals are included in the surface irradiatedwith the beam. Alternatively, a flat target may have surface roughnesswhich is about the size of the beam diameter.

In a columnar target, a normal common to the substrate surface and thetarget surface can be defined. If it is defined that the intersectionbetween the common normal and the target is the foot of the normal, aplume is hardly generated to the direction of the substrate unless thefoot is irradiated with the part of the laser beam.

The same applies to a target having a polygonal cross section. FIG. 62shows this state. When the target is polygonal, it is at first placed sothat there is a common normal, and then it is set such that the foot ofthis normal is irradiated by a part of the laser beam, whereby a plumecan be generated to the direction of the substrate.

FIG. 63 shows an example in which the incident angle θ₀ of the beam isset to 0. It is described above that the incident angle should be madesmaller. However, if it is made too small, substrate 2 and laser beam 16interfere with each other. In order to prevent the interference, thetarget and the substrate 2 may be placed apart. However, depending onthe target material, the plume is small and in such a case, the distancecannot be increased.

Therefore, there is provided an aperture in substrate 2, so that laserbeam 16 passes through the opening. FIG. 64 shows an example in whichlaser beam 16 is focused near the aperture, so that the diameter of theopening can be reduced. An aperture or a notch may be provided at an endof the substrate through which the beam passes. In either case, thoughthe shape of the substrate is somewhat limited, a thin film can beformed uniformly over a wide area.

FIG. 65 shows the state of a columnar target irradiated with the beam.Plumes are generated in the form of a fan along the normals of thecolumn. Therefore, a thin film is formed in the region shown by the dotsin the figure. In order to form the thin film uniformly over thesubstrate, it is necessary to rotate the substrate or the target.Uniformity of the thin film is expected even when a spherical target isused, if its rotated.

FIG. 66 shows an example in which substrates 2a and 2b are fixed on aholder 4222 having an aperture. Since a number of substrates arearranged, thin films can be formed efficiently.

FIG. 67 shows an example in which the target is rotated while it ismoved in parallel, in order to prevent reduction in the angle ofextension of the plume caused by the wear of the target. The angle ofextension of the plume can be kept constant by constantly renewing thesurface of the target which is irradiated with a laser beam 16 by suchan operation. The parallel movement can be carried out in the similarmanner even when the target is a flat plate or a sheet.

A thirty-fifth embodiment of the present invention will be describedwith reference to FIG. 68. In the figure, the same reference charactersas in FIG. 148 denote the same or corresponding portions.

In this embodiment, referring to FIG. 68, a substrate holder 111 whichis a polygonal cylinder is placed around a raw material target 110 whichhas a cylindrical shape. At least two substrates 2 are placed on theinner side of the substrate holder 111, that is, the side opposing tothe raw material target 110. Laser beam 16 emitted from laser unit 10 iscondensed by a condenser lens 9, reflected by a mirror 8, passed throughinlet window 7 and directed to raw material target 110. At a portion ofraw material target 110 which is irradiated with the laser, a plasma isgenerated abruptly, forming a plume 15. At this time, raw materialtarget 110 rotates and is moved parallel in the direction of the axis ofrotation. Accordingly, raw material target 110 can be thoroughlyirradiated with a laser beam 16. This prevents uneven wear of the rawmaterial target 110. At the same time, substrate holder 111 is rotatedand moved parallel to the direction of the axis of rotation.Consequently, the plume 15 generated from that portion of raw materialtarget 110 which is irradiated with laser beam 16 sweeps the substrate 2entirely. Consequently, distribution of thin film on substrate 2 can beimproved, enabling formation of a thin film over a wide area. Since twoor more substrate 2 are placed on substrate holder 111, throughput inthin film formation can be improved.

A thirty-sixth embodiment of the present invention will be describedwith reference to FIG. 69. FIG. 69 is a schematic diagram showing thestructure of the thin film forming apparatus using laser in accordancewith one embodiment of the present invention. In the figure, referencecharacters 1 to 17 denote the same or corresponding portions in FIG. 148of the prior art.

Referring to FIG. 69, in the present embodiment, laser beam 16 emittedfrom laser unit 10 passes through laser inlet window 7 of chamber 1,then it is introduced into chamber 1 through the center of substrateholder 3 in chamber 1 to be incident on raw material target 5 placed onturntable 11 in chamber 1.

Consequently, a plume is generated and a thin film is deposited onsubstrate 2, in the similar manner as in the above described prior art.However, in this embodiment, laser beam 16 is introduced through thecenter of substrate holder 3. Therefore, laser beam 16 is incident ontarget 5 vertically. The extension of plume generated from target 5becomes larger as the incident angle of laser beam incident on thetarget becomes smaller. Therefore, according to this method, theextension of the plume can be maximized. Consequently, a thin filmhaving large area can be obtained most efficiently. In this embodiment,a thin film can be formed over the area of 20 mm×20 mm (with thevariation of film thickness distribution being ±10%) without effectingXY driving of the substrate. Thus, it is proved that by this method, athin film having larger area than in the prior art can be formed.

A thirty-seventh embodiment of the present invention will be describedwith reference to FIG. 70. FIG. 70 is a schematic diagram showing thethin film forming apparatus using laser in accordance with oneembodiment of the present invention. In the figure, reference characters1 to 17 denote the same or corresponding components as in the prior artexample of FIG. 148.

In this embodiment, referring to FIG. 70, laser beam 16 emitted fromlaser unit 10 is condensed by condenser lens 9 and passed through laserinlet window 7 of chamber 1 to be incident on raw material target 5placed on turntable 11 in chamber 1.

Consequently, a plume is generated and a thin film is deposited on thesubstrate 2, in the similar manner as in the aforementioned prior artexample. However, different from the prior art example, in thisembodiment, the point of focus 133 of the condensed laser beam 16 is setin front of the surface of target 5. As shown in FIG. 70, when thesubstrate 2 is placed at this point of focus, the laser beam will beincident on target 5 vertically through substrate 2 and substrate holder3, and the size of the hole provided in substrate 2 can be minimized.This enables deposition of a thin film over a wide area of substrate 2,realizing thin film formation over a wide area. In this embodiment, athin film can be formed over the area of 20 mm×20 mm (with variation offilm thickness distribution being ±10%) without effecting XY driving ofthe substrate. Therefore, it is proved that by this method, a thin filmcan be formed over wider area than in the prior art. Since the energy ofthe laser beam is concentrated on this point of focus, the introducedgas such as oxygen is activated, and therefore, active substances can besupplied without using high energy particles such as ion beams.Consequently, a thin film of high quality can be formed without usingthe ion beam.

In the above described embodiment, the beam is directed to target 5through substrate holder 3 and substrate 2. However, even when the laserbeam is emitted from different direction or when the point of focus 133is not at the position of the substrate, the effect of improving qualityof the thin film by activation of the introduced gas can be similarlyobtained.

A thirty-eighth embodiment of the present invention will be describedwith reference to FIG. 71. FIG. 71 is a schematic diagram showing thethin film forming apparatus using laser in accordance with oneembodiment of the present invention. In the figure, reference numerals 1to 17 denote the same or corresponding components as in the prior artexample.

Referring to FIG. 71, in this embodiment, laser beam 16 emitted fromlaser unit 10 is condensed by condenser lens 9 and passed through laserinlet window 7 of chamber 1 to be incident on raw material target 5placed on turntable 11 in chamber 1.

Consequently, a plume is generated and a thin film is deposited onsubstrate 2 in the similar manner as in the above described prior artexample. However, different from the prior art example, in thisembodiment, the point of focus 133 of the condensed laser beam 16 isplaced on the surface of target 5. Then, plume 15 is generated from anextremely small region of target 5 so that energy density gradient onthe target surface is large. Consequently, the direction of scatteringof the particles included in the plume varies wider. Consequently, ascompared in the example in which the point of focus of the laser beam isnot on the target surface, the plume comes to have wider extension.Consequently, a thin film can be deposited on wider area of substrate 2,realizing formation of a thin film having large area. In thisembodiment, a thin film can be formed over the area of 20 mm×20 mm (withvariation of film thickness distribution being ±10%) without effectingXY driving of the substrate. Thus, it is proved that by this method, athin film having larger area than the prior art can be formed.

A thirty-ninth embodiment of the present invention will be describedwith reference to FIG. 72. In this embodiment, referring to FIG. 72, notonly an evacuating apparatus 17 but also an evacuating apparatus 179 fordifferential evacuation provided near target 5 are operated, andtherefore the degree of vacuum is made uniform over wider area near thetarget 5. Therefore, when the target 5 is irradiated with laser beam 16,the scope of generation of the plume 15 can be enlarged. Since a thinfilm is formed on substrate 2 which is in contact with plume 15, auniform thin film can be formed over wider area as the scope ofgeneration of plume 15 becomes larger.

A fortieth embodiment of the present invention will be described withreference to FIG. 73. In this embodiment, referring to FIG. 73, laserbeam 16 emitted from laser unit 10 is condensed by condenser lens 9, andpassed through laser inlet window 7 of chamber 1 to be incident on rawmaterial target 5 placed on turntable 11 of chamber 1. Substrate 2 isplaced fixed on substrate holder 3, opposing to raw material target 5.Excited atoms and ions of plume 15 reach the substrate 2. Meanwhile,hydrogen atoms are supplied from hydrogen ion source and hydrogenradical source 103 to the substrate, so that they are deposited on thesurface of growth. Further, kinetic energy of hydrogen is applied to theatoms and molecules on the surface of growth. Consequently, surfacemigration of these growing particles is promoted. Therefore, a thin filmis deposited and formed with superior property of crystals with lesspoint defects and lattice defects even at a relatively low temperature.

A forty-first embodiment of the present invention will be described withreference to FIG. 74. In FIG. 74, laser beam 16 is transmitted to aportion of a conduit of a gas supply nozzle 130 and passed through awindow 131 to be incident on target 5. Meanwhile, gas is suppliedthrough gas supply nozzle 130 to be blown over substrate 2.

Operation will be described. The gas in gas supply nozzle 130 isactivated by laser beam 16 and blown over substrate 2. Therefore,activated gas can be supplied to the vicinity of substrate 2 withoutacceleration by voltage. Accordingly, a thin film having high qualitycan be formed without damaging the substrate 2.

A forty-second embodiment of the present invention will be describedwith reference to FIG. 75. Referring to FIG. 75, a half mirror 132 isprovided in gas supply nozzle 130. Most part of laser beam 16 is passedthrough half mirror 132 and through window 131 to be incident on target5. Gas supply nozzle 130 is adapted such that a part of the laser beam16 is reflected by half mirror 132.

The operation will be described. Laser beam 16 transmitted through halfmirror 132 sputters the target 5, while laser beam 16 reflected fromhalf mirror 132 activates the gas in gas supply nozzle 130. Since thegas activated by laser beam 16 blows over substrate 2 through gas supplynozzle 130, a thin film having high quality can be formed withoutdamaging substrate 2.

A forty-third embodiment of the present invention will be described withreference to FIG. 76. The apparatus of the present embodiment includes,referring to FIG. 76, a rotary mesh electrode 921 which can be placedparallel to the substrate, and a ground line 922 for grounding thesubstrate and the substrate holder.

The operation will be described. Before starting film formation, rotarymesh electrode 921 is rotated to be horizontally placed over a substratewhich is grounded, and power is input from an RF power supply so as togenerate plasma between the mesh and the substrate. By maintainingplasma for several minutes, the substrate is cleaned. Then, the power isstopped and the mesh electrode is rotated downward to be away from thesubstrate. Thereafter, the target is irradiated with laser to form afilm on the cleaned substrate.

According to this embodiment, in an apparatus for forming, byirradiating a target with laser, a film on an opposing substrate, thesubstrate is cleaned by discharge before film formation. Therefore, athin film forming apparatus using laser by which a thin film havingsuperior film characteristics than in the prior art can be formed, isobtained.

A forty-fourth embodiment of the present invention will be described. Inthis embodiment, music is played instead of a chime or buzzer at thestart or end of a process. The music may be a short phrase or a tune.The music may end after a while, or it may be continued. By providing anadjusting element for changing the sound volume, volume appropriate foreach environment can be selected. Not only music but also messageprovided by synthetic voice may be given.

The music may be changed from process to process, and the message givenby synthetic voice may be changed according to the process. For example,different tunes may be used when loading/unloading of a sample iscompleted or when the film formation is completed. When messages areused, clear and definite message may be used at important processes, andsoft and short message may be given for other processes not so importantso that the message would not be noisy.

Since one have his or her own favorite music, not the one specific musicbut several tunes or melodies may be selected as desired. The messagesmay also be selected similarly. For example, male or female voice, highor low tone, soft manner of speaking or strict manner of speaking may beselected.

A forty-fifth embodiment of the present invention will be described withreference to FIG. 77. The apparatus of this embodiment includes,referring to FIG. 77, a mirror moving apparatus 220, an XYθ stage 221for moving the target, a sample moving apparatus 221, a DC sputteringapparatus 223, an RF sputtering apparatus 224, an RF reverse sputteringapparatus 225, a shutter 226, a movement controlling apparatus 227 andan ion beam sputtering apparatus 228.

The operation will be described. By setting the distance between target5 and substrate 2 wider than the diameter of target 5, plume 15 comes tobe extended more easily, so that the film can be made uniform over widerarea. If this distance is shorter than the diameter of the target, thespace in which the plume is generated becomes elongate in FIG. 120, andtherefore the plume hardly extends. However, if the distance is longerthan the diameter of the target, the space in which the plume isgenerated will be wide in the lateral direction in FIG. 220. Therefore,the plume expands easily, so that the film can be easily made uniformedover wider area.

In FIG. 77, a plurality of lasers are used to increase the number ofplumes generated at one time. This facilitates uniform film formationover wider area. Since the rate of film formation is increased as thenumber of lasers is increased, the throughput is improved.

In the structure of FIG. 77, the mirror, the target and the sample canbe moved. By moving these, film can be formed uniformly. Such movementis controlled by movement control apparatus 227 which allows movement atrandom, simple rotation as well as rotation and revolution.

In the structure of FIG. 77, DC or RF can be applied so as to assist thelaser or as the pre-processing of the substrate and the target. When RFis applied to the substrate with the shutter 226 closed, the substratecan be cleaned, and the surface of the target can be cleaned. By suchoperation, a highly pure thin film can be formed. When DC or RF isapplied so as to assist the laser, or by utilizing ion beam sputteringas well, the rate of film formation can be improved, and the film can bemade uniform over wider area.

A forty-sixth embodiment of this invention will be described withreference to FIGS. 78 and 79. The apparatus of this embodiment includes,referring to FIG. 78, a target holder 281 having a path 282 of coolingwater, a thermocouple 283 for monitoring the temperature of the holder,and a chiller 284 for controlling the flow rate and the temperature ofthe cooling water. In the figure, the same reference characters as inFIG. 188 denote the same or corresponding portions.

The operation will be described. When a film is formed on an opposingsubstrate 2 by irradiating target 5 with laser beam 16, part of theoptical energy of 16 laser incident on target 5 turns to heat. As thefilm formation is continued, the temperature of target 5 increasesgradually as shown in FIG. 79. However, at this time, target holder 281is maintained at a constant temperature, as cooling water, which has itstemperature controlled by chiller 284, flows through cooling water path282. Consequently, target 5 is cooled by target holder 281, and theincrease of temperature stops after a prescribed period as shown in FIG.79 and it can be kept at a constant state from relatively earlierperiod.

As described above, by this embodiment, time change of the temperatureof the target can be suppressed, and therefore thin film formingapparatus using laser enabling continuous film formation at an optimaltarget temperature can be provided.

A forty-seventh embodiment of the present invention will be describedwith reference to FIG. 80. FIG. 80 is a schematic diagram showing thelaser thin film forming apparatus in accordance with this embodiment. Inthis embodiment, referring to FIG. 82, in the vicinity of raw materialtarget 5, a high frequency induction coil 920 for generating highfrequency induction electric-magnetic field is provided. The point offocus of condenser lens 9 is set at a position shallower than in theconventional apparatus, and the diameter of the laser beam 16 formed ontarget 5 is ten times that of the prior art.

The function of the thin forming apparatus using laser will bedescribed. The target used in this embodiment is a copper target 5having the purity of 99.9%. First, substrate 2 is held by substrateholder 3, the chamber 1 is evacuated to vacuum (1×10⁻⁴ Torr), and thenhigh frequency current of 10 MHz is applied for 0.5 sec to highfrequency induction coil 920. And then laser beam is emitted. (Thoughfrequency of 10 MHz is used here, frequency higher than 1 MHz ispreferred since efficiency in heating is higher). Here, simultaneouslywith the laser beam irradiation, plume 15 is generated on target 5.After the laser beam is kept emitted for 30 seconds, the laser beam andthe high frequency current are stopped and substrate 2 is taken out fromthe chamber 1 after substrate 2 is cooled sufficiently. A copper thinfilm formed on the surface of substrate 2 is observed.

In the above embodiment, when laser beam irradiation is carried outwithout conducting high frequency induction coil 920, plume 15 is notgenerated on target 5. A copper thin film is not formed on the surfaceof substrate 2 at this time.

In the above described embodiment, when laser beam is not emitted andhigh frequency induction coil 920 is kept conductive for 30.5 seconds,plume 15 is not generated on target 5. At this time, thin film of copperis not formed on the surface of substrate 2.

By using a conventional thin film forming apparatus using laser, laserbeam irradiation is kept for 30 seconds, then laser beam is stopped andsubstrate 2 is taken out from chamber 1 after it is pulled. Whenobserved, there is formed a copper thin film on the surface of substrate2. However, the diameter of copper thin film formed is 1/15 that of thefilm formed in the above described embodiment.

As described above, according to this embodiment, since high frequencyinduction coil 920 for generating high frequency inductionelectric-magnetic field is provided near raw material target 5, someenergy can be applied to the surface of raw material target 5.Therefore, plasma can be easily formed on raw material target 5 evenwith an energy density lower than the energy density of the laser beamused in the conventional thin film forming apparatus using laser. As aresult, laser beam having large area can be directed to the surface ofraw material target 5, and a thin film having large area can be easilyformed.

A forty-eighth embodiment of the present invention will be describedwith reference to FIG. 81. Referring to FIG. 81, the apparatus of thepresent embodiment includes a cooling fin 4401 as a mechanism forcooling substrate 2, a substrate support portion 4402 for supportingsubstrate 2 as well as cooling fin 4401, a target base 4403 on whichtarget 5 is placed, a target support 4404 for supporting target 5 aswell as target 4403, infrared laser beam or far infrared laser beam 4405for heating substrate 2, lens 9b for condensing infrared laser beam orfar infrared laser beam 4405, and infrared laser beam or far infraredlaser beam 4406.

The operation is as follows. As described above, laser beam emitted fromlaser unit 10 is condensed by condenser lens 9 and passed through laserinlet window 7 of chamber 1 to be incident on raw material target 5placed in chamber 1. At the portion of raw material target 5 which isirradiated with laser, plasma is generated abruptly, and in the processof cooling the plasma for several ten ns, isolated excited atoms andions are generated. These excited atoms and ions have lives of at leastseveral microseconds, and they are emitted to the space to form a plume15 which is like a flame of a candle. A substrate 2 is placed fixed onsubstrate holder 3 opposing to raw material target 5. The excited atomsand ions in plume 15 reach the substrate 2 and are deposited thereon,forming a thin film.

In order to form a thin film of superior quality, it is necessary toheat the substrate 2 so as to anneal the film which has been depositedat a low temperature at a temperature higher than the temperature forcrystallization, or to form crystallized thin film at the site byholding the substrate itself at a temperature higher than thetemperature for crystallization at the time of deposition. In theconventional film forming apparatus, a heater is provided adjacent tothe substrate as shown in FIG. 148 for heating the substrate. Thesubstrate 2 as a whole is heated by this heater. Since the conventionalapparatus has such a structure, portions not requiring heating of thesubstrate are also heated, which caused degradation of the substrate ordegradation of the function of the thin film.

In this embodiment, as shown in FIG. 81, infrared laser or far infraredlaser unit 4406 such as represented by carbon dioxide laser or YAG laseris provided. The infrared laser beam or far infrared laser beam 4405emitted from the laser unit 4406 is condensed by lens 9b to be incidenton substrate 2. Consequently, substrate 2 can be heated locally. By thisheat, annealing of the film and formation of crystallized thin film canbe carried out. When infrared laser or far infrared laser is used as thelaser unit 4406, the heat can be well conducted in the depth directionof the substrate. When only the vicinity of the surface of the substrate2 is to be heated, ultraviolet laser may be used as the laser unit 4406.

Further, in this embodiment, there is provided a cooling film 4401 as amechanism for cooling substrate 2, provided adjacent to substrate 2, asshown in FIG. 81. Even if substrate 2 is heated by using condensedinfrared laser or far infrared laser, generated heat may possibly reachportions which do not require heating on the substrate dependent on thetime of laser beam irradiation or the like, which may cause degradationof substrate or the function of the thin film. In this embodiment, inorder to solve this problem, the portion requiring heating of substrate2 is heated by laser beam 4405, while portions not requiring heating ofthe substrate 2 are cooled by fin 4401. Consequently, the heat generatedcan be prevented from reaching portions which do not require heating ofthe substrate, and hence degradation of substrate or the function ofthin film caused by heat can be prevented.

When only a minute pattern on substrate 2 is to be annealed, coolingmechanism 4401 may be provided at a portion other than the minutepattern so as to more effectively prevent the influence of heat. Thougha fin is used as cooling mechanism 4401 in this embodiment, a Peltierelement or the like may be used to provide the same effect.

A forty-ninth embodiment of the present invention will be described withreference to FIG. 82.

The apparatus of this embodiment includes, referring to FIG. 82, amirror 4407 for changing optical path of infrared laser beam or farinfrared laser beam 4405 for heating substrate 2, a mirror controllingportion 4408 for controlling orientation of mirror 4407, a mirror 4410for changing optical path of laser beam 16 directed to target 5, and amirror controlling portion 4411 for controlling orientation of mirror4410.

The operation is as follows. As described above, by using mirror 4410,only a portion which should be heated to high temperature of substrate 2can be heated. However, when there are a plurality of portions which areto be heated on the substrate, it is difficult to locally heat theseportions requiring heat by a structure in which laser beam 4405 isdirected to a certain point. This problem becomes more serious when thesubstrate 2 has an area as large as 6 to 8 inches in diameter.

In this embodiment, a mechanism for adjusting the position ofirradiation of the substrate with infrared laser beam or far infraredlaser beam is provided. FIG. 182 shows an example in which portion ofirradiation of substrate 2 with infrared laser beam or far infraredlaser beam is adjusted by changing the optical path of infrared laserbeam or far infrared laser beam 4405.

When a film is to be formed on a wafer having large area, for example,having a diameter of 6 to 8 inches or larger, it is not possible to formthe film entirely over the wafer when only one plume 15 is generated atone point of target 5. Therefore, plumes 15 must be generated at aplurality of portions of target 5. For example, in FIG. 82, a mirror4410 for changing the optical path of laser beam 16 with which thetarget 5 is irradiated, and a mirror controlling portion 4410 forcontrolling the direction of mirror 4410 are provided. By changing theorientation of mirror 4410 so that the position of irradiation of thetarget 5 with the laser beam 16 is changed, plumes 15 are generated at aplurality of portions on target 5. Further, in the structure of FIG. 82,the position of irradiation of substrate 2 with infrared laser beam orfar infrared laser beam can be adjusted by changing the optical path ofinfrared laser beam or far infrared laser beam 4405. Laser 4405 emittedfrom the infrared laser unit or the far infrared laser unit is reflectedby mirror 4407 and condensed by lens 9b to be incident on substrate 2.Here, a mirror controlling portion 4408 is provided at mirror 4407 forcontrolling orientation of mirror 4407. By this mirror controllingportion 4408, the orientation of mirror 4007 can be changed. Therefore,position to be locally heated of substrate 2 can be changed inaccordance with the change of position of irradiation of the target 5with the laser beam 16.

As described above, in the present embodiment, the position ofirradiation of the substrate with infrared laser beam or far infraredlaser beam can be adjusted, and in addition, the substrate is cooled bycooling fin 4401. Therefore, increase of temperature at a portion whichdo not require heat on substrate can be effectively suppressed. Further,by arbitrarily moving infrared laser beam or far infrared laser beam onthe substrate, a minute pattern on the surface of substrate 2 can beannealed.

When the range of adjustment of the position of irradiation of thesubstrate with the infrared laser beam or the far infrared laser beam isof innegligible size as compared with the focal length of lens 9b, thelaser beam may be out of focus on the substrate when the position oflaser irradiation is changed. This may cause unnecessary heating ofportions of the surface of substrate 2 by laser beam 4405. In such acase, a lens position adjusting portion 4409b may be provided at lens 9bas shown in FIG. 84. The lens position adjusting portion 4409 adjuststhe position of the lens or the angle with respect to laser beam 4405 inaccordance with the change in position of irradiation of the substratewith infrared laser beam or far infrared laser beam 4405. Therefore,necessary area of the laser beam can be obtained on substrate 2. Such alens position adjusting portion may be provided at condenser lens 9a forlaser beam 16 which is directed to target 5. In that case, the laserbeam can be prevented from being out of focus on target 5. Consequently,variation in conditions of generation of plume 15 caused by the changein laser power density per unit area can be prevented.

In the above described embodiment, the optical path of infrared laserbeam or far infrared laser beam 4405 is changed for adjusting theposition of irradiation of substrate 2 with infrared laser beam or farinfrared laser beam 4405. However, a mechanism for changing the positionof substrate 2, such as shown in FIG. 83 may be provided. The apparatusshown in FIG. 83 includes a substrate driving portion 4412 for changingthe position of substrate 2, a connecting plate 4413 for connectingsubstrate driving portion 4412 and cooling fin 4401, and a targetdriving portion 4414 provided between target base 4403 and targetsupport 4404.

The operation will be described. In the example of FIG. 83, in order togenerate plumes 15 at a plurality of portions of target 5, not theoptical paths of laser beams 16 and 4405 but positions of target 5 andsubstrate 2 are changed. For example, laser beam 16 is condensed by thelens to be incident on target 5, a plume 15 is generated and a film isdeposited on substrate 2. Then, target driving portion 4414 andsubstrate driving portion 4412 are driven to change positions of target5 and substrate 2. Consequently, laser beam 4405 is directed to adifferent position from the last time of substrate 2 and heat thatportion of substrate 2. Thereafter, by condensing laser beam 16 by thelens again to be incident on the target 5, plume 15 is generated, andfilm can be formed on a new position of substrate 2. In this manner, theposition for local heating of substrate 2 can be changed in accordancewith the change in position of irradiation of the target 5 with laserbeam 16.

As described above, in this embodiment, by changing the position ofsubstrate 2, the position of irradiation of the substrate with infraredlaser beam of far infrared laser beam can be adjusted. In addition,since the substrate is cooled by cooling fin 4401, increase intemperature of portions which do not require heating on the substratecan be effectively suppressed. By arbitrarily scanning the substrate 2and target 5, a pattern on the surface of substrate 2 can be annealed.

A fiftieth embodiment of the present invention will be described withreference to FIG. 85. The apparatus of this embodiment includes,referring to FIG. 85, a plume monitoring port 4421 for monitoring plume15 from outside of chamber 1, a plume monitoring window 4422 attached toplume monitoring port, a plume monitoring portion 4423 for monitoringplume 15, a control portion 4425 which receives information of the plumeobtained from plume monitoring portion 4423 for outputting a signal forcontrolling position of substrate 2 or target 5, a signal line 4424a fortransmitting the output signal from plume monitoring portion 4423 tocontrolling portion 4425, a signal line 4424b for transmitting theoutput signal from control portion 4425 to target position drivingportion, a target position adjusting table 4426 for adjusting theposition of target 5, and a target position driving portion 4427receiving the signal from controlling portion 4425 for moving the targetposition adjusting table.

The operation is as follows. As described above, laser beam 16 emittedfrom laser unit 10 is condensed by condenser lens 9 and passed throughlaser inlet window 7 of chamber 1 to be incident on raw material target5 placed in chamber 1. Thus a plume 15 is generated in a directionvertical to target 5. A substrate 2 is placed fixed on substrate holder3, opposing to raw material target 5. Excited atoms and ions in plume 15reach the substrate 2 and are deposited thereon to form a thin film.

Here, target 5 is irradiated with the laser beam repeatedly for a numberof times. Therefore, the surface of the target 5 is gradually removed sothat the surface becomes less planar. For this reason, when laser beamirradiation is repeated for a number of times, the position ofgeneration of plume 15 may be displaced, or the plume 15 may begenerated not to the direction of substrate 2. Further, as laser beamirradiation proceeds, there will be deposits on window 7a so that thetransmittance of window 7a is reduced. In addition, the power of thelaser beam incident on target 5 may be gradually lowered due to thecharacteristics of the laser unit and the like. In such a case, the sizeof the generated plume 15 is also reduced. Therefore, in theconventional film forming apparatus, the position and size of the plumegenerated may be changed as the laser beam irradiation proceeds, whichleads to unevenness of film thickness of reduction in the late of filmformation.

In order to solve the above described problem, in this embodiment, amechanism for changing the position of the target or the substrate inaccordance with the change in position of the plume is provided. In thisembodiment, referring to FIG. 85, an image sensor, for example, isprovided. Plume monitoring portion 4423 monitors position and size ofthe plume generated from target 5, and the information is transmittedthrough signal line 4424a to controlling portion 4425. Controllingportion 4425 determines whether the plume is generated at an appropriateposition with an appropriate size, based on the information from plumemonitoring portion 4423. If the position of the plume is notappropriate, it provides a signal to target 4427 through signal line4424b so that the target driving portion 4427 is moved to realizeappropriate relation between substrate 2 and the position of generationof the plume. In response, target position driving portion 4427 movestogether with target position adjusting table 4426, target base 4403 andtarget 5, so that substrate 2 and the position of plume generation haveappropriate relation. If the size of the plume is not appropriate,similar operation as above is carried out to adjust the distance betweentarget 5 and substrate 2, so as to compensate for the change in distancebetween plume and the substrate caused by the changed in the size of theplume.

By the above described operation, positional relation between the plumeand the target can be kept constant, and therefore deviation of theplume position and unevenness of the film quality caused by the changein the size of the plume can be prevented.

Although the position of target 5 is controlled in accordance with thechange in position or size of the plume in the above describedembodiment, the position of the substrate 2 may be controlled. FIG. 86shows such an example. The apparatus shown in FIG. 86 includes asubstrate position driving portion 4428 attached to substrate holder 3.In this example, control signal from controlling portion 4425 istransmitted to substrate position driving portion 4428 through signalline 4424b. In response, substrate position driving portion 4428 movestogether with substrate holder 3 and substrate 2, so that the substrate2 and the position of plume generation satisfy an appropriate relation.If the size of the plume is not appropriate, similar operation asdescribed above is carried out to adjust the distance between target 5and substrate 2, so as to compensate for the change in distance betweenthe plume and the substrate caused by the change in the size of theplume.

As described above, in the example shown in FIG. 86 also, the positionalrelation between the plume and the target can be kept constant.Therefore, deviation in the position of the plume and unevenness of thefilm quality caused by the change in the size of the plume can beprevented.

Although an image sensor is used in plume monitoring portion 4423 in theabove described embodiment, a camera, a video camera, a probe or thelike may be used as the plume monitoring portion 4423 to provide thesame effect.

Though a mechanism for changing the position of the target or thesubstrate in accordance with the change in position of the plume isprovided in the above described embodiments, a mechanism for changingthe optical path of the laser in accordance with the change in theposition of the plume may be provided.

A fifty-first embodiment of the present embodiment will be describedwith reference to FIGS. 87 and 88. The apparatus of this embodimentincludes a mirror 4431 provided in the optical path of the laser beam 16emitted from laser unit 10, and a mirror angle adjusting portion 4430attached to mirror 4431.

The operation is as follows. As described above, as the film formingoperation is continued, the position of generation of the plume 15 maybe displaced a little, or the plume 15 may be generated not to thedirection of substrate 2. In this embodiment, the optical path of thelaser is changed as the position of the plume changes, so as tocompensate for the change in position of the plume. In this embodiment,referring to FIG. 88, an image sensor is provided, for example. Plumemonitoring portion 4423 monitors the position of the plume generatedfrom target 5, and the information is transmitted through signal line4424a to controlling portion 4425. Controlling portion 4425 determineswhether or not the plume is generated at an appropriate position, basedon the information from plume monitoring portion 4423. If the positionof the plume is not appropriate, it transmits a signal to mirror angleadjusting portion 4430 through signal line 4424b so that the laser beamincident on target 5 is positioned appropriately. In response, mirrorangle adjusting portion 4430 adjusts the angle of mirror 4431 so that anappropriate position of target 5 is irradiated with laser beam 16. Bythis operation, plume can be generated at a prescribed positionconstantly, and unevenness of film quality caused by the change in thesize of the plume can be prevented.

If the range of adjustment or the position of irradiation of target 5with laser beam 16 is of innegligible size as compared with the focallength of lens 9b, the laser beam may be out of focus on target 5, whenthe position of laser irradiation is changed. Consequently, the laserbeam intensity may possibly be reduced on the surface of target 5,resulting in the change of size of the generated plume. In such a case,a lens position adjusting portion 4432 may be provided at lens 9b asshown in FIG. 88. Lens position adjusting portion 4432 is controlledtogether with mirror angle adjusting portion 4430, so that the positionof the lens and the angle of the lens with respect to laser beam 4405can be adjusted in accordance with the change of position of irradiationof the target 5 with laser beam 16. Consequently, necessary area oflaser beam can be obtained on target 5, whereby conditions forgenerating the plume 15 can be prevented from being uneven.

A fifty-second embodiment of the present invention will be describedwith reference to FIG. 89. In this embodiment, referring to FIG. 89, alaser power adjusting portion 4429 is attached to laser unit 10.

The operation is as follows. As descried above, when film formingoperation is continued, there will be deposits on window 7a causinglower transmittance of window 7a, and the power of the laser beamincident on the target 5 may be gradually lowered due to thecharacteristics of the laser unit and the like. In that case, the sizeof the plume 15 generated is also reduced. Therefore, in theconventional film forming apparatus, the size of the plume may bechanged, causing unevenness of the film thickness and reduction in therate of film formation.

In order to solve the above described problems, in this embodiment, amechanism for changing the power of the laser beam in accordance withthe change in the position of the plume is provided. Referring to FIG.89, in this embodiment, a plume monitoring portion 4423 provided with animage sensor, for example, monitors the size of the plume generated fromtarget 5, and the information is transmitted through signal line 4424ato control portion 4425. Control portion 4425 determines whether or notthe plume is generated with an appropriate size based on the informationfrom plume monitoring portion 4423. If the intensity of the laser beamincident on target 5 has been changed and the size of the plume is notappropriate, it transmits a signal to laser power adjusting portion 4429through signal line 4424b, so that the intensity of the laser beamincident on target 5 is made appropriate. In response, laser poweradjusting portion 4429 controls laser unit 10 such that the laser unit10 emits the laser beam having appropriate intensity. As for the meansfor changing output intensity of laser unit by laser power adjustingportion, the voltage of discharge for laser excitation may be changed,or a part of the laser beam may be intercepted by an aperture.Alternatively, the number of repetition of the pulse laser may bechanged.

By the above described operation, a plume having a constant size can begenerated, and therefore unevenness of the film quality caused by thechange in the size of the plume can be prevented.

A fifty-third embodiment of the present invention will be described withreference to FIG. 90. Referring to FIG. 90, the apparatus of thisembodiment includes a target height adjusting table 4415 for adjustingthe height of target 5, a target height adjusting driving portion 4416for moving upward and downward the target height adjusting table 4415for adjusting the height of target 5, a mirror 4417 for reflecting laserbeam entering the chamber, a mirror attaching plate 4418 for attachingmirror 4417, and a mirror based 4419 supporting the mirror attachingplate.

The operation is as follows. As described above, laser beam 16 emittedfrom laser unit 10 is condensed by condenser lens 9, and passed throughlaser inlet window 7 of chamber 1 to be incident on raw material target5 placed in chamber 1. At the portion of raw material target 5irradiated with laser, a plasma is generated abruptly, and in theprocess of cooling the plasma in several ten ns, isolated excited atomsand ions are generated. These groups of excited atoms and ions havelives of at least several microseconds and they are emitted to the spaceto form a plume 15 which is like a flame of a candle. Substrate 2 isplaced fixed on substrate holder 3, opposing to raw material target 5.Excited atoms and ions in plume 15 reached the substrate 2 and aredeposited thereon to form a thin film.

Here, not all the excited atoms and ions emitted to the space fromtarget 5 reach the substrate 2, and part thereof reach other portions ofchamber 1. A part of excited atoms and a part of ions reach innersurface of window 7a provided at the chamber to be deposited thereon.Therefore, as the film forming apparatus is used, there will be depositson inner surface of window 7a, decreasing transmittance of window 7a.

In this embodiment, as shown in FIG. 90, a mirror 4417 is provided forreflecting laser beam 16 which has entered the chamber 1 to direct thebeam to window 7a of the chamber. In this structure, the position oftarget 5 can be changed by target height adjusting table 4415, andtarget height adjusting driving portion 4416. When a film is to beformed on substrate 2, generally, target 5 is placed at a position wheretarget 5 can be irradiated with laser beam 16. When there is substancesdeposited on window 7a, target height adjusting table 4415 is lowered bytarget height adjusting driving portion 4416, so that laser beam 16 canreach mirror 4417. At this time, laser beam 16 reflected by mirror 4417reaches inner surface of window 7a so as to turn the deposits on theinner surface of window 7a into plasma, so that the deposit is removed.Consequently, the transmittance of window 7a can be recovered withoutopening the chamber. When a concave mirror is used as mirror 4417 sothat the light reflected from mirror 4417 is condensed on window 7a,removal of the deposit can be carried out more efficiently.

A fifty-fourth embodiment of the present invention will be describedwith reference to FIG. 91. In this embodiment, referring to FIG. 91, amirror angle adjusting portion 4420 for adjusting the angle of mirror4117 is provided. In the fifty-third embodiment described above, mirror4417 is fixed on mirror attaching plate 4418. Therefore, the laser beamreflected by mirror 4417 will be incident on the same position on innersurface of window 7a constantly. If the size of the beam of thereflected light incident on the inner surface of window 7a is largeenough to cover the size of the laser beam incident on window 7a, thereis no problem. However, if the size of the beam of the reflected lightwhich is incident on the inner surface of window 7a is not large enoughto cover the size of the incident laser beam on window 7a, or when thereflected light is condensed small on the inner surface of window 7a inorder to improve the effect of removal, the deposit on the window 7acannot be fully removed from the entire portion through which incidentlaser beam 16 passes, by the structure of the above embodiment.

The present embodiment is to solve this problem, and it includes amechanism for changing the position of irradiation of the window withthe reflected beam of the laser beam introduced to the chamber.Referring to FIG. 91, mirror 4417 is attached on mirror angle adjustingportion 4420. By this mirror angle adjusting portion 4420, the angle ofmirror 4417 with respect to the incident angle of laser beam 16 can bechanged. Consequently, the position of irradiation of the inner surfaceof window 7a with the reflected beam from mirror 4417 can be changed,and therefore deposit can be fully removed from the entire portion ofwindow 7a through which incident laser beam 16 passes. A control systemmay be provided at mirror angle adjusting portion 4420 so that aninstruction for adjusting the mirror angle is transmitted to mirrorangle adjusting portion 4420 from the outside of the chamber.

A fifty-fifth embodiment of the present invention will be described withreference to FIGS. 92, 93A and 93B. The apparatus of this embodimentincludes, referring to FIG. 92, a target 4433 having an opening throughwhich laser beam is passed, a target support 4434 for supporting target4433 having the opening, a target base 4435 for supporting a pluralityof target supports 4434, and a spacer 4436 provided between substrateholder 3 and substrate support portion 4402.

The operation is as follows. As described above, laser beam 16 emittedfrom eraser unit 10 is condensed by condenser lens 9 and passed throughlaser inlet window 7 of chamber 1 to be incident on raw material target5 placed in chamber 1. At the portion of raw material target 5irradiated with laser, a plasma is generated abruptly, and in theprocess of cooling the plasma in several ten ns, isolated excited atomsand ions are generated. These groups of excited atoms and ions havelives of at least several microseconds, and they are emitted to thespace to form a plume 15 which is like a flame of a candle. Substrate 2is placed fixed on substrate holder 3, opposing to raw material target5. Excited atoms and ions of the plume 15 reach the substrate 2 and aredeposited thereon to form a thin film.

Now, in this embodiment, a target 4434 having an opening through whichthe laser beam is transmitted such as shown in FIGS. 93A and 93B is usedas the target. A plurality of such targets 4433 having openings aresupported by target supports 4434 as shown in FIG. 92. The targetsupports 4434 are connected to target base 4435 having a driving portiontherein. For example, in FIG. 92, target supports 4434 and targets 4433having openings are adapted to be rotated by the driving portion intarget base 4435. These targets 4433 having openings are arranged suchthat by rotating respective targets, laser beam 16 is directed toanother target through the opening of one target.

For example, when laser beam 16 is directed to a portion other than theopening of the first target 4434 having the opening, a plume 15 isgenerated from the first target 4433 having the hole, and film is formedat that portion of the surface of substrate 2 which is near the plume.When laser beam 16 passes through the opening of the first target 4433to be directed to a portion other than the opening of the second target4433 having the opening, a plume 15 is generated from the second target4433 having the opening and a film is formed at that portion of thesurface of substrate 2 which is near the plume. Similarly, when laserbeam passes through the openings of first to nth targets 4433 havingopenings and directed to a portion other than the opening of the n+1thtarget 4433 having the opening, a plume 15 is generated from the n+1thtarget 4433, and a film is formed at that portion of the surface ofsubstrate 2 which is near the plume. In this manner, by introducing onlyone laser beam to chamber 1, plumes 15 can be generated from a pluralityof targets, and therefore a film can be formed over wide area on thesurface of substrate 2. Although a rotating mechanism is used forchanging the position of the targets in the above described embodiment,a mechanism for horizontal movement or vertical movement may be used toprovide the same effect.

When the area for forming film on the substrate 2 is very large and alarge number of targets 4433 having openings are to be used, thedistance between respective targets and the substrate differ from targetto target, which may cause unevenness in film thickness and film qualityof the film formed on the substrate 2. In order to prevent this problem,a spacer 4436 may be provided so that the distance between each of thetargets 4433 having openings and substrate 2 is kept constant, as shownin FIG. 92.

In the above described embodiment, a plurality of targets havingopenings through which laser beam is transmitted were used as targetsfor laser sputtering, and the targets are arranged such that laser beamis directed to another target through the opening of one target bychanging the positions of the targets. Now, in FIG. 92, when thedistance between the target which is closest to the laser beam inletwindow 7 to the target which is the farthest from window is long ascompared with the focal length of the lens 9, for example, the area ofcondensation of the laser beam on each target differs from target totarget to an extent too large to neglect. At this time, because of thedifference in the area of condensation of the laser beam, the laser beamintensity per unit area incident on its target differs, which results indifference in the size of the plume generated at each position. Thiscauses unevenness in film thickness and composition of the thin filmformed on the substrate 2. Therefore, the difference in laser beamintensity per unit area incident on these targets must be suppressed to5% at most.

In order to solve this problem, a lens having long focal length is usedas the condenser lens for laser beam. For example, as shown in FIG. 98,when a lens having short focal length as compared with the distancebetween targets 4433a and 4433b is used as condenser lens 9, there willbe a large difference between the diameter a of the condensed beam ontarget 4433a and the diameter b of the condensed beam on target 4433b.Therefore, a lens having such a focal length which suppresses thedifference in the area of condensed beam on the targets becomes 5% atmost of the area of condensation of the smallest point of condensation,as condenser lens 9. By using such a lens, the square of the differencebetween diameters a to d of the condensed beams on targets 4433a to4433d can be suppressed to 5% at most, and the difference in laser beamintensity at respective points of condensation can be suppressed to 5%at most. Thus, the size of plume generated at respective points ofcondensation can be made uniform.

A fifty-sixth embodiment of the present invention will be described. Theapparatus of this embodiment includes, referring to FIGS. 94A to 94D, apolygonal target 4437 and a bar shaped target 4438 provided on targetsupport 4434, respectively.

The operation will be described. In the above described embodiment,targets 4433 having openings through which laser beam is transmittedsuch as shown in FIG. 93 were used as the target. In this embodiment, aplurality of targets other than a target having an opening are used, sothat plumes are generated from a plurality of portions by using only onelaser beam. FIGS. 94A to 94D show an example in which triangular targetis used as the polygonal target. The polygonal target is supported bytarget support 4434 as in the example shown in FIG. 93. The targetsupport 4434 is connected to target base 4435 having a driving portiontherein. In FIGS. 94A to 94D, for example, target supports 4434 andtriangular targets 4437 are adapted to be rotated by the driving portionin target base 4435. The triangular targets 4437 are arranged such thatby rotating each target, the laser beam 16 passes the side of one targetto be incident on another target. For example, in FIGS. 94A to 94D,triangular target 4437 is supported by target support 4434 at the pointof the center of gravity of the triangle, and rotates with the center ofgravity of the triangle being the center. Here, the distance between thecenter of gravity to a vertex is longer than the distance from thecenter of gravity to one side, in a triangle. Therefore, when thetriangular target is rotated such that the laser beam is incident nearthe vertex of the triangle, the laser beam is incident on the targetwhen a portion near the vertex of the triangle comes to the position ofthe laser beam, while the laser beam is not incident on that target whena portion near one side of that target comes to the position of thelaser beam, and the laser beam is incident on another target. FIG. 94Bis a front view showing one example, and FIG. 94A is the front viewthereof. Referring to FIG. 94B, the laser beam 16 is introduced from theupper left side. Though triangular targets 4437a to 4437c are rotated ontarget support 4434, at the moment shown in FIG. 94B, the portion ineach of the triangular targets 4437a to 4437c which is closest to thelaser beam 16 is, in triangular target 4437a, a side, in triangulartarget 4437b, a side, and in triangular target 4437c, a vertex.Therefore, laser beam passes outside of the sides of triangular targets4437a and 4437b and directed to a portion near the vertex of thetriangular target 4437c. Thus, a plume 15 is generated from triangulartarget 4437c. At the moment shown in FIG. 94C, the portion closest tolaser beam 16 of each of triangular targets 4437a to 4437c is, intriangular target 4437a, a side, in triangular target 4437b, a vertex,and in triangular target 4437c, a side. Therefore laser beam 16 passesthe outside of the side of triangular target 4437a and directed to thevicinity of vertex of 4437b. Thus plume 15 is generated from triangulartarget 4437b. By controlling rotation of each target, a plume can begenerated from a plurality of portions by one laser beam 16, and a filmcan be formed over a wide area on substrate 2.

Though polygonal shaped targets are used in the example of FIGS. 94A to94D, a bar shaped target may be used. FIGS. 96A to 96B show such anexample. In FIGS. 96A and 96B, 4438 denote bar shaped targets. The barshaped targets 4438 are supported by target supports 4434 as in theexample shown in FIGS. 94A to 94D. The target supports 4334 areconnected to target base 4335 having a driving portion therein. In FIGS.96A and 96B, for example, target supports 4434 and bar shaped targets4438 are adapted to be rotated by the driving portion in target base4435. These bar shaped targets are arranged such that when each of thetargets is rotated and the longitudinal direction of a bar shaped targetand the direction of the optical path of the laser beam 16 coincide witheach other, laser beam 16 is incident on the target 4438, while when thelongitudinal direction of the bar shaped target and the direction of theoptical path of laser beam 16 do not coincide with each other, the laserbeam 16 passes aside the target to be incident on another target. FIG.96B is a front view showing one example thereof, and FIG. 96A is planview. Referring to FIG. 96B, laser beam 16 is introduced from upper leftside.

Bar shaped targets 4438a to 4438c are rotated on target support 4434. Atthe moment shown in FIGS. 96A and 96B, as for the longitudinal directionof the bar shaped targets 4438a to 4438c and the optical path directionof laser beam 16, the longitudinal direction and the direction of theoptical path of the beam do not coincide in the case of bar shapedtarget 4438a, the directions do not coincide in the case of bar shapedtarget 4438b either, but the longitudinal direction of bar shaped target4438c coincides with the direction of the optical path. Therefore, laserbeam 16 does not directed to bar shaped two targets 4438a and 4438b, butit is directed to the bar shaped target 4438c. Thus a plume 15 isgenerated from bar shaped to target 4438c. By controlling rotation ofthe targets, plumes can be generated from a plurality of portions by onebeam 16, and therefore a film can be formed over wide area on substrate2.

Though a mechanism for rotation is used for changing the positions oftargets in the above described embodiment, a mechanism for horizontalmovement or vertical movement may be used to provide the same effect.FIG. 97 shows an example employing a mechanism for vertical movement. Inthe example of FIG. 97, bar shaped targets 4438 are attached to barshaped target support 4434. The target support 4434 are connected to atarget base 4435 having a driving portion therein. In FIG. 97, targetsupport 4434 and bar shaped target 4438 are adapted to move in thevertical direction indicated by the arrow 4439 by means of the drivingportion in the target base 4435. When a target which is closest to laserinlet window 7 is placed on the optical path of the laser beam 16, thelaser beam is incident on the target, and the plume is generated fromthis target. When the target closest to the laser inlet window 7 islowered away from the optical path of the laser beam 16 and the targetsecond closest to the laser inlet window 7 is placed on the optical pathof the laser 16, laser beam 16 is incident on this target and the plumeis generated from this second closest target. Similarly, when all thetargets from the closest one to the nth closest target to the laserinlet window 7 are lowered away from the optical path of laser beam 16and the n+1th closest target from the laser inlet window 7 is placed onthe optical path of the laser 16, laser beam 16 is directed to thetarget n+1th-closest to laser inlet window 7, and the plume is generatedfrom this target. By controlling the positions of these targets in thismanner, plumes can be generated from a plurality of portions by onelaser beam 16, and a film can be formed over wide range on the surfaceof substrate 2.

A fifty-seventh embodiment of the present invention will be describedwith reference to FIG. 99. FIG. 99 is an illustration showing theoperation of this embodiment. Referring to FIG. 99, the laser beam 16 isdirected to target 5 with an incident angle of θ. First, a point a oftarget 5 is irradiated with laser beam 16. At this time, plume 15a isgenerated from this point a, and a film is formed near a point a' ofsubstrate 2 by this plume 15a. When the laser beam 16 is continuouslydirected to target 5, the surface of target 5 is removed with time. Therate of removal of target 5 in the depth direction y is represented asdy/dt=b (t).

Assume that a film is formed over a scope having the length of x in atime period t≦t0. Irradiation of point a with laser beam 16 is startedat time t=0, and irradiation is continued to time t=t0. At this time,the depth y of removal of target 5 in the depth direction from time t=0to t=t0 corresponds to the value obtained by time integral of the rateof removal dy/dt=b (t) of target 5 in the direction of the depth y fromt=0 to t=t0. As the target 5 is removed, except in the case that theincident angle of laser beam 16 with respect to target 5 is 0, thetarget is removed also in the horizontal direction, and therefore theposition of irradiation on target 5 with laser beam 16 is deviatedgradually. The distance x0 of removal of target 5 in horizontaldirection from time t=0 to t=t0 is represented as x0=y0/tan (90°-θ)where y0 represents the removal of target 5 in the depth direction y.

When laser beam 16 is continuously emitted to target 5, at time t=0, thebeam is incident on point a of target 5, and the position of irradiationchanges as time passes and the beam is incident on point b which isapart from point a by the distance x0 at time t=t0. Accordingly, theposition of the plume generated on target 5 changes from point a topoint b accordingly, so that a film can be formed over point a' to b' onsubstrate 2 during this period. Therefore, when a film is to be formedover an area having the length x for a time t≦t0, the laser beam 16should be directed to target 5 with an incident angle θ which issatisfies x≦y0/tan (90°-θ) so that the film can be formed over theprescribed area by the movement of the plume, utilizing the removal oftarget 5. In this manner, by introducing only one laser beam 16 intochamber 1, the position of plume 15 can be changed, and the film can beformed over a large area on substrate 2. When the area of film formationover substrate 2 is large and the distance between the substrate and theposition of generation of each plume differs from plume to plume to aninnegligible extent, film thickness and film quality may possibly bemade uneven. In order to solve this problem, a spacer 4436 may beprovided as shown in FIG. 92 so as to keep constant the distance betweentarget 5 and substrate 2 constant.

A fifty-eighth embodiment of the present invention will be describedwith reference to FIG. 100. In the figure, the same reference charactersas in FIGS. 148 and 149 denote the same or corresponding portions.

The operation will be described. The laser beam emitted from laser unit10 is condensed by condenser lens 9 and passed through laser inletwindow 7 of chamber 1 to be incident on raw material target 5 placed onturntable 11 of chamber 1. At the portion of raw material target 5irradiated with laser, plasma of the target material is generatedabruptly at the time of laser irradiation, and in the process of coolingthe plasma in several ten ns, isolated groups of excited atoms,molecules and ions are generated. These groups of excited atoms,molecules and ions have lives of several microseconds and they areemitted in the space to form a plume 15 which is like a flame of acandle.

Substrate 2 is placed fixed on substrate holder 3 opposing to rawmaterial target 5. Excited atoms, molecules and ions in the plume andthe target material in the shape of clusters which are combinations ofthese atoms and ions reach the substrate 2 and are deposited andcrystallized thereon to form a thin film, as in the prior art.

Meanwhile, radiation beam 308 is directed to the surface of substrate 2during, during and after, or before, during and after laser beamirradiation of raw material target 5.

When the surface of the substrate 2 is irradiated with the radiationbeam 308 during, or during and after irradiation of target 5 with laserbeam 16, state of electrons of the atoms at the substrate surface areresonantly excited in non-equilibrium by radiation beam 308 which is ahigh energy continuous spectrum beam having its peak of light intensityat the range of soft X-ray to vacuum ultraviolet wavelength. Inaddition, atoms, molecules and clusters of the target raw material whichhave been generated by the irradiation of target 5 with laser beam 16and have reached the surface of substrate have their states of electronsresonantly excited in non-equilibrium. Consequently, crystallization ofthe target material in the form of atoms, molecules and clusters on thesubstrate surface is promoted in non-thermal equilibrium, and thereforea thin film having high quality can be grown at a low temperature.

When the surface of substrate 2 is irradiated with radiation beam 309before irradiation of target 5 with laser beam 16, state of electrons ofatoms molecules constituting an impurity thin film formed on the surfaceor impurity particles deposited on the surface are resonantly excited innon-equilibrium, which promotes removal and elimination of the impurityparticles or impurity thin film on the surface of the substrate 2.Accordingly, prior to the formation of a film by the target material onthe substrate surface, a clear substrate surface is exposed. Therefore,initial nucleus of the thin film of the target material is generated onthe pure and clean substrate surface without any impurities, andtherefore thin film of the target material has the crystals grownregularly in the subsequent steps, and thus a thin film of high qualitycan be formed in a pure states with less problem of the interfaceimpurities on the substrate.

A heater 4 for heating the substrate is provided in substrate holder 3.This enables post annealing in which the film deposited at a lowtemperature is annealed at a temperature higher than the temperature forcrystallization to provide a thin film of high quality, and it alsoenables as-deposition in which the substrate itself is kept at atemperature higher than the temperature for crystallization at the timeof deposition so that a crystallized thin film is formed at that site.In as-deposition method, active oxygen atmosphere is utilized as well.For example, when an oxide thin film is to be formed, a nozzle 6 forsupplying gas 19 containing oxygen is provided as shown in the figure,so as to provide oxygen atmosphere near substrate 2, so as to promotegeneration of the oxide on substrate 2, as in the prior art.

In the above described fifty-eighth embodiment, radiation beam is used.However, instead of the radiation beam, vacuum ultraviolet laser beamsuch as fluorine (F2) laser, argon-fluorine (ArF) laser and the like,vacuum ultraviolet lamp such as xenon (Xe) lamp, deuterium (D₂) lamp andthe like, or X-ray laser beam may be used to provide the same effect.

A fifty-ninth embodiment of the present invention will be described withreference to FIG. 111. In the present embodiment, referring to FIG. 101,prior to film formation on the substrate opposing to the target by laserbeam irradiation, a movable concave mirror 262 is rotated so that thesubstrate is irradiated with the laser beam and the substrate surface isheated, thereby cleaning the substrate surface. Thereafter, the movableconcave mirror is rotated again so that the target is irradiated withthe laser beam for film formation. Since the substrate is cleaned beforefilm formation, impurity and foreign matters deposited on the substratesurface are removed, and therefore a film having superior property andless impurity can be formed. When a flat mirror is used as the mirrorfor reflecting the laser beam, a large area can be irradiated bychanging the angle of the mirror a little, and therefore large area ofthe substrate can be cleaned and the film is formed. When a concavemirror is used as the mirror for reflecting the laser beam, irradiationof a large area of the target as well as of the substrate is possible.This time, if the movable concave mirror is positioned at anintermediate position between the target surface and the substratesurface, adjustment of the beam diameter when the destination of thebeam is changed become unnecessary.

A sixtieth embodiment of the present invention will be described withreference to FIG. 102. In this embodiment, referring to FIG. 102, priorto film formation on the substrate opposing to the target by laser beamirradiation, a movable mirror 263 is inserted to the optical path of thelaser so that the substrate is irradiated with the laser beam, and thesubstrate surface is heated. Thus the substrate surface is cleaned.Thereafter, the movable mirror 263 is moved again to be out of theoptical path of the laser beam, and the target is irradiated with thelaser beam and the film is formed. Since the substrate is made cleanbefore film formation, impurities and foreign matters deposited on thesurface of the substrate are removed. Consequently, a film havingsuperior properties and less impurities can be formed. As mentionedabove, the first concave mirror for laser beam irradiation is movable,so that large area of the target as well as of the substrate can beirradiated.

A sixty-first embodiment of the present invention will be described withreference to FIG. 103. Referring to FIG. 103, the apparatus of thisembodiment includes a first raw material target 500, a second rawmaterial target 501 and a turntable 503 on which the first and secondraw material targets 500 and 501 are mounted. In this embodiment, SrTiO₃single crystal substrate is used as substrate 2, BaTiO₃ is used as thefirst material target 500, and Ba₀.5 Sr₀.5 TiO₃ is used as the secondraw material target 501. In the figure, the same reference characters asin FIGS. 148 and 149 denote the same or corresponding portions.

The operation is as follows. First, turntable 503 is rotated so thatBa₀.5 Sr₀.5 TiO₃ target, which is the second raw material target 501 ismoved to a position opposing to SrTiO₃ single crystal substrate 2.Second target 501 is irradiated only once with pulse laser beam, so thata (Ba, Sr) TiO₃ the composition of which is very close to that of thetarget, is deposited to about 10 nm on the substrate 2. Thereafter,turntable 503 is rotated again to select BaTiO₃, which is the first rawmaterial target 500. Irradiation with pulse laser beam is repeated, anda BaTiO₃ film of a desired thickness is deposited on the (Ba, Sr) TiO₃film. The above described steps were carried out under reduced pressurein an oxygen atmosphere, and a BaTiO₃ epitaxial film with less defectcan be obtained even when the substrate temperature is decreased to aslow as about 500° C.

As described above, in this embodiment, a plurality of raw materialtargets are placed on a disk, and by rotating the disk, an arbitrary rawmaterial target can be irradiated with the pulse laser beam. Sincemovement of the raw material target is in synchronization with the pulselaser beam, the raw material target can be changed for everyirradiation. Since the raw material target can be arbitrarily changed inthe process of film formation in this manner, when a film havingdifferent lattice constant from the underlayer is to be formed, a bufferlayer having an intermediate lattice constant may be formed by using adifferent raw material target, and thereafter a desired film can beformed continuously. Further, it is expected that the thin filmdeposited by the thin film forming apparatus using laser has itscomposition changed quite a little from the composition of the target.Therefore, the lattice constant can be delicately controlled.Accordingly, through the above described steps, a film having superiorproperty of crystals can be obtained at low substrate temperature.Accordingly, degradation of the substrate and degradation of thefunction of the thin film caused by undesirable side reaction derivedfrom high temperature for forming the film on the substrate can beprevented.

Provision of a film having superior crystal property at low substratetemperature by continuously forming the buffer layer and the thin filmwhich is the original object, realized by the present embodiment, isespecially useful in fabricating a perovskite type single crystal thinfilm which is mainly consisting of titanate such as BaTiO₃ which is usedas a dielectric film of a thin film capacitor of highly dielectric body.

For example, conventionally, a BaTiO₃ thin film capacitor or the likehas been in most cases formed by using SrTiO₃ or Pt used as a lowerelectrode. However, in that case, there is lattice mismatch of about 2to 3% between BaTiO₃ and the lower electrode. Therefore, if depositionis carried out in this state, an epitaxial film having superior crystalproperty cannot be obtained unless the substrate temperature isincreased to as high as about 900° C.

A sixty-second embodiment of the present invention will be describedwith reference to FIG. 104. The apparatus of this embodiment includes,referring to FIG. 104, a first raw material target 500, a second rawmaterial target 501, a third raw material target 502, a shaft 504mounting the raw material targets, and a shaft controlling apparatus 505for controlling rotation and parallel movement of the shaft. In thisembodiment, a Si wafer is used as the substrate 2, BaTiO₃ is used as thefirst raw material target 500, Ba₀.5 Sr₀.5 TiO₃ is used as the secondraw material target 501, and Pt is used as the third raw material target502. In the figure, the same reference characters as in FIGS. 418 and149 denote the same or corresponding portions.

The operation will be described. First, the shaft 504 is moved in theaxial direction and Pt, which is the third raw material target 502, ismoved to a position opposing to substrate 2. Pulse laser irradiation isrepeated so that a Pt film is deposited on an upper portion of Si wafer.Thereafter, shaft 504 is again moved in the axial direction, and Ba₀.5Sr₀.5 TiO₃ target, which is the second raw material target 501, isirradiated only once by the pulse laser beam. Consequently, a (Ba, Sr)TiO₃ film having the composition very close to that of the target isdeposited on substrate 2 to the thickness of about 10 nm. Thereafter,shaft 504 is again moved in the axial direction so as to select BaTiO₃,which is the first raw material target 500. By pulse laser irradiation,a BaTiO₃ film having a desired thickness is deposited on the (Ba, Sr)TiO₃ film. The above described steps were carried out under reducedpressure in an oxygen atmosphere, and a BaTiO₃ epitaxial film havingless defect could be formed as in the above described embodiment, evenwhen the substrate temperature is decreased to as low as about 500° C.

Though only one layer of (Ba, Sr) TiO₃ is used as the buffer layerenabling epitaxial growth of the BaTiO₃ film in the above describedembodiment, the property of crystal of the BaTiO₃ can be furtherimproved by using a plurality of layers having lattice constantsslightly different from each other. This can be realized by arranging adesired number of raw material targets in the thin film formingapparatus using laser, and operating these in synchronization with thelaser, so that a desired raw material target can be selected. In theforegoing, means to obtain a BaTiO₃ film having superior crystalproperty has been described. However, such means is also effective informing other films of crystal property at a low temperature.

A sixty-third embodiment of the present invention will be described withreference to FIG. 105. The apparatus of this embodiment includes,referring to FIG. 105, an oxygen gas supply source 506 and an ECR plasmachamber 507. In this embodiment, a silicon substrate coated withplatinum is used as the substrate 2, and BaTiO₃ is used as raw materialtarget 5. In the figure, the same reference characters as in FIGS. 148and 149 denote the same or corresponding portions.

The operation will be described. The oxygen gas supplied from the oxygengas supply source first enters the ECR plasma chamber. There is anelectrostatic field in the ECR plasma chamber, and microwave power isapplied to this chamber. By the functions of these, a so-called ECRplasma derived from cyclotron movement of the oxygen gas is generated,and therefore active oxygen ions are generated. The oxygen gas activatedin this manner is introduced to a film forming chamber. Under such afilm forming atmosphere, BaTiO₃, as the raw material target wasirradiated with the laser, and a thin film was formed. A BaTiO₃ thinfilm having smaller defects could be formed even when the substratetemperature was decreased to as low as about 500° C.

Though ECR plasma was used for ionizing the oxygen gas, similar effectis expected when RF plasma is used. Similar effect is also expected whenoxygen gas is excited by irradiation with UV light. Though oxygen wasused for oxidizing gas in this embodiment, an organic substance such asalcohol including oxygen may be used. Nitrogen gas may be used foroxidization in its broader meaning. Further, such effect is obtained notonly in forming BaTiO₃ film but also in forming other oxide thin film.

As described above, the oxidizing gas in this embodiment is suppliedfrom an oxidizing gas supply source and ionized in a preceding chamberprovided for the purpose of activating the oxidizing gas such as an ECRplasma chamber, and then introduced to the thin film forming chamber. Anoxide film is deposited by using laser in such an active oxidizing gasatmosphere. Since such active oxidizing gas is supplied to the filmforming chamber, the oxygen defect generated during film deposition canbe immediately repaired by the oxygen ions supplied from the activeoxidizing atmosphere. Therefore, an oxide film having superior crystalproperties with smaller oxygen defect can be obtained even at a lowtemperature. Accordingly, degradation of the substrate and degradationof the function of the thin film caused by undesirable side reactionderived from high temperature for film formation of the substrate can beprevented. The ionized oxidizing gas introduced to the film formingchamber do not have such high kinetic energy as the ion beam, andtherefore the damage to the substrate is negligible.

Provision of an oxide film having superior quality at a low substratetemperature by introducing the oxidizing gas to the film forming chamberafter the gas is activated, such as realized by the present embodiment,is especially advantageous in fabricating a perovskite type thin filmmainly consisting of titanate such as BaTiO₃ used as a dielectric filmof a thin film capacitor of highly dielectric body. Conventionally, ithas been difficult to form a highly insulative BaTiO₃ thin film at a lowtemperature. This is because the oxygen defects generated duringdeposition of the film cannot be easily repaired when the film isdeposited at a low temperature. When the film is formed at a hightemperature, there have been problems of mutual diffusion of compositionelements at the interface between the formed film and a platinum filmwhich is mainly used as the lower electrode, and degradation ofinsulation derived therefrom.

A sixty-fourth embodiment of the present invention will be describedwith reference to FIG. 106. The apparatus of this embodiment includes,referring to FIG. 106, an oxygen gas supplying source 506 and a DC powersupply 508 for applying a DC voltage to the substrate. In thisembodiment, a silicon substrate coated with platinum is used assubstrate 2, and BaTiO₃ is used as raw material target 5. In the figure,the same reference characters as in FIGS. 148 and 149 denote the same orcorresponding portions.

The operation will be described. First, while a prescribed positive biasis being applied to the substrate, the raw material target is irradiatedwith the laser beam, thus a plume is generated, and the film isdeposited on the substrate placed near the plume. At this time, oxygenions generated by the reaction with the plume are collected near thesubstrate as they are attracted by the positive potential of thesubstrate and these ions contribute to repair oxygen defect during filmformation. By such an operation, a BaTiO₃ thin film could be obtainedwith smaller defects even when the substrate temperature was decreasedto as low about 500° C.

Though a DC potential is applied to the substrate in this embodiment, anAC potential such RF may be applied. Similar effect can be expected byexcitation of the oxygen gas by UV irradiation. Though oxygen was usedas oxidizing gas in this embodiment, an organic substance containingoxygen such as alcohol may be used. Nitrogen gas may be used foroxidation in its broader meaning. Further, such effect is provided notonly in forming the BaTiO₃ film but also in forming other oxide thinfilms.

As described above, the thin film forming apparatus using laser inaccordance with this embodiment is structured such that at the time ofdepositing an oxide film, an oxidizing gas is introduced to the filmforming chamber, and when the raw material target is irradiated with thelaser beam and there is generated a plume between the raw materialtarget and the substrate, a DC or RF potential is applied between thesubstrate and the ground potential or between the substrate and the rawmaterial target. When a DC positive potential or the like is applied tothe substrate, for example, the oxidizing gas which has been ionized bythe reaction with the radical seeds and the like in the plume near thesubstrate will be incident on the substrate surface with an appropriateenergy. Such ion seeds repair the oxygen defects which are caused duringfilm deposition. Therefore, an oxide film having superior crystalproperty with smaller oxygen defects can be obtained even when thesubstrate temperature is low. Accordingly, degradation of the substrateand the degradation of the function of the thin film caused byundesirable side reaction derived from high temperature for filmformation of the substrate can be prevented. In addition, the kineticenergy of the oxidizing gas which has been ionized and guided near tothe substrate can be made small enough not to damage the substrate, byappropriately adjusting the substrate potential.

Provision of an oxide film having superior quality at low substratetemperature by applying a DC or RF potential to the substrate and byguiding ion seeds generated in the reaction with the plume to thesubstrate surface, such as realized by the present invention, isespecially useful in fabricating perovskite type thin film may beconsisting of titanate such as BaTiO₃ which is used as a dielectric filmof a thin film capacitor of a highly dielectric body. Generally, it hasbeen difficult to form a highly insulative BaTiO₃ thin film at a lowtemperature. The reason for this is that the oxygen defects generatedduring film deposition is hardly repaired if the film is deposited at alow temperature. When the film is formed at a high temperature, therehave been problems of mutual diffusion of composition elements at theinterface between the film and the platinum film mainly used as thelower electrode, and degradation of insulation derived therefrom.

A sixty-fifth embodiment of the present invention will be described withreference to FIG. 107. The apparatus of this embodiment includes,referring to FIG. 107, a mirror 509 for excimer laser, and an etchinggas supply source 510. In this embodiment, a silicon wafer is used assubstrate 2, a phosphorus doped silicon is used as raw material target,excimer laser is used as laser beam 16, and hydrofluoric acid vapor isused as etching gas. In the figure, the same reference characters as inFIGS. 148 and 149 denote the same or corresponding portions.

The operation will be described. In order to clean the surface of thesilicon wafer prior to film formation, etching gas is introduced to thefilm forming chamber, the laser beam has its optical path changed by amirror inserted to the optical path, and the substrate surface isirradiated with the laser beam. By the heat caused by the laser beam,organic contamination is removed by combustion. At the same time,natural oxide is removed by hydrofluoric acid, and thus a clear surfaceis obtained. Thereafter, the film forming chamber is evacuated to highvacuum, the mirror is removed so that the optical path of the laser ischanged to the side of the target. By laser irradiation of raw materialtarget, a polycrystalline silicon thin film is deposited. After the filmdeposition, in order to reduce resistance value by improving crystalproperty, the optical path of the laser is again changed, and the filmsurface is irradiated with the laser. By forming a polycrystallinesilicon film in this manner, contact resistance and the wiringresistance could be reduced.

Though etching gas is introduced in the above described embodiment,similar effect of cleaning the substrate surface can be obtained bylaser irradiation in vacuum. Although a mirror is used for changing theoptical path of the laser, the optical path may be changed by moving thelaser, moving the film forming chamber or by rotation of a lens.

As described above, in the thin film forming apparatus using laser inaccordance with this embodiment, a excimer laser beam having high energydensity is used, and the apparatus is structured such that the substratesurface can be irradiated with laser by switching the laser opticalsystem. Consequently, by irradiating the substrate surface with laserbefore film deposition, clear substrate surface can be obtained withoutincreasing the substrate temperature. By forming a desired filmthereafter, the interface with less impurities can be obtained. Byirradiating the film surface with the laser beam after the film isformed at a low temperature, the crystal property of the deposited filmcan be improved without degrading the substrate.

Cleaning of the substrate surface before deposition and improvement ofthe crystal property of the deposited film by irradiation of substratesurface with the laser beam such as realized by the present invention isespecially useful in fabricating a polycrystalline silicon thin film forsemiconductor memory devices. Conventionally, when in formingpolycrystalline silicon wiring formed at the contact portion with thesilicon substrate, light etching of the surface by hydrofluoric acidcontained solution or a so-called in-situ cleaning in the film formingapparatus have been carried out in order to reduce impurities at theinterface in order to reduce contact resistance, light etching is not soeffective against contamination caused by the combination of organicdeposition and natural oxide film. Further, a new natural oxide film maybe grown until the substrate is set to the film forming apparatus. Asfor the in-situ cleaning, a temperature as high about 1000° C. isnecessary. In order to reduce film resistance of the polycrystallinesilicon film for wiring, dopant is introduced after film formation andthen heated to a high temperature of about 900° C. However, provision ofpolycrystalline silicon film having low film resistance at lowertemperature has been strongly in demand.

Sixty-sixth embodiment of the invention will be described with referenceto FIG. 108. In FIG. 108, the same portions as in the prior art exampleof FIG. 148 are denoted by the same reference characters and descriptionthereof will not be repeated.

In this embodiment, referring to FIG. 108, the laser beam emitted fromlaser unit 10 and sputtering target 5 is reflected from the surface ofthe target to be turned to scattered laser beam 752, and detected by adetector 751 through an outlet window 750. At that time, as theunevenness on the target surface becomes larger, the detection intensityof the scattered laser beam decreases. Therefore, in-situ, that is, atthe site of forming the laser thin film, the state of erosion of thetarget surface can be known, and therefore formation of uneven filmcaused by surface roughness of the target can be prevented.

A sixty-seventh embodiment of the present invention will be describedwith reference to FIG. 109. In FIG. 109, the same components as in theprior art example of FIG. 148 are denoted by the same referencecharacters and description thereof is not repeated. The apparatus ofthis embodiment includes, referring to FIG. 109, an inlet window 753 ofx-ray or electron beam, an outlet window 754 of characteristic x-ray, anapparatus for generating the x-ray or electronic beam, and aspectroscope 756 for the characteristic x-ray.

The operation is as follows. In synchronization with the laser beam 16emitted from the laser unit and sputtering the target 5, acharacteristic x-ray 758 inherent to the atoms constituting the targetis generated by x-ray or electronic beam 757 emitted ram a x-ray orelectronic beam generating apparatus 754. The characteristic x-ray 758passes through outlet window 754 and is divided and detected by x-rayspectroscope 756, whereby qualitative and quantitative analysis of thetarget composition is carried out. Therefore, during the process offorming a thin film by using laser, the composition of the region of thetarget which is being sputtered can be known at that site. Therefore,formation of an uneven film caused by the change in composition of thetarget can be prevented.

A sixty-eighth embodiment of the present invention will be describedwith reference to FIG. 110. In FIG. 110, the same portions as in theprior art example of FIG. 148 are denoted by the same referencecharacters and description thereof will not be repeated. The apparatusof this embodiment includes, referring to FIG. 110, a half mirror 700for dividing the laser beam, a polarizer 701 for polarizing the dividedlaser beam, and a detector 702 for ellipsometer.

The operation is as follows. The laser beam 16 emitted from laser unit10 and sputtering target 5 has its part divided by half mirror 700 andpassed through polarizer 701 so that the beam has polarizationcharacteristics and then it is directed to a film 702 formed onsubstrate 2. The laser beam reflected from the film surface is detectedby detector 703 for the ellipsometer. By the polarization analysis ofthe detected laser beam, the thickness of the film which is being formedcan be monitored at that site during the process of forming a thin filmusing laser. In addition, the result of analysis can be fedback to thesputtering conditions, whereby the film thickness can be controlled.

A sixty-ninth embodiment of the present invention will be described withreference to FIG. 111. In FIG. 111, the same components as in the priorart example of FIG. 148 are denoted by the same reference characters anddescription thereof will not be repeated. The apparatus of thisembodiment includes, referring to FIG. 111, a rotatable half mirror 704for dividing the laser beam, a polarizer 705 which moves insynchronization with the rotation of the half mirror for polarizing thedivided laser beam, a film formed by the thin film forming apparatus byusing laser, and a detector 306 for an ellipsometer which moves insynchronization with the rotation of half mirror 704.

The operation is as follows. The laser beam 16 emitted from laser unit10 and sputtering target 5 is partially divided by a rotating halfmirror 704, and the divided beam is passed through a polarizer 705 whichmoves in synchronization with the rotation of the half mirror so that ithas polarization characteristics. The film 702 formed on the substrate 2is scanned and irradiated by this beam by the rotation of the halfmirror. The laser beam reflected from the surface of this film isdetected by detector 706 for the ellipsometer which also moves insynchronization with the rotation of half mirror. By polarizationanalysis of the detected laser beam, the film thickness distribution ofthe film being formed can be monitored at the site during the process offorming the thin film by using laser. In addition, the result ofanalysis can be fedback to the sputtering conditions, so that the filmthickness and film thickness distribution can be controlled.

A seventieth embodiment of the present invention will be described withreference to FIG. 112. In FIG. 112, the same component as in the priorart example shown in FIG. 148 are denoted by the same referencecharacters and description thereof will not be repeated. Referring toFIG. 112, the apparatus of this embodiment includes a window 21 formonitoring generation of the plume, a spectroscope 22 for dividing andmeasuring the light generated from the plume, an optical fiber 23 forguiding the light generated from the plume to the spectroscope 22; anoptical fiber support portion 24 for supporting one end of optical fiber23 so that if faces window 21, a position adjusting mechanism 25 formoving optical fiber support portion 24, an analyzing apparatus 26 foranalyzing the information obtained from spectroscope 22, and acontrolling apparatus 27 for controlling film parameters based on theresult of analysis obtained from analyzing apparatus 26.

The operation is as follows. In the thin film forming apparatus usinglaser structured as described above, optical fiber 23 supported byoptical fiber support portion 24 is moved by adjusting positionadjusting mechanism 25, light from various portions of the plume 15 istaken out from the chamber 1 through window 21, and the light isdirected to spectroscope 22 through optical fiber 23. By analyzing lightemission spectrum of the plume obtained from the spectroscope 22, typesand ratio of particles playing important roles in forming the thin filmsuch as activated neutral seeds and ion seeds at the state of highexcitation in plume 15 can be recognized. By controlling parameters forfilm formation by using controlling apparatus 27 based on the result ofanalysis obtained from analyzing apparatus 26, the state of the plume 15can be kept constant. Accordingly, a film having superior quality withuniform composition and smaller impurities or proper orientation can beformed.

A seventy-first embodiment of the present invention will be describedwith reference to FIG. 113. In the figure, the same components as in theprior art shown in FIG. 148 or the seventieth embodiment shown in FIG.112 are denoted by the same reference characters and description thereofwill not be repeated. The apparatus of this embodiment includes,referring to FIG. 113, an analyzing apparatus 26 for analyzing infraredabsorption spectrum, an infrared light source 28, an inlet window 30 forintroducing the infrared ray 29 to the inside of the film formingapparatus using laser, a fixed mirror 31 for changing the direction ofthe infrared ray 29, a movable mirror 32 for providing optical paths sothat the infrared ray (incident light) 29 passes through variousportions of plume 15, a moving apparatus 33 for changing position of themovable mirror 32, a time division Fourier transform infraredspectrometer 35 for spectroscopic measurement of the infrared ray(transmitted light) transmitted through plume 15, and an outlet window36 for guiding the infrared ray (transmitted light) 34 to the infraredspectrometer 35.

The operation is as follows. In the thin film forming apparatus usinglaser structured as described above, the infrared ray (incident light)29 emitted from infrared light source 28 enter through inlet window 30and passes through the optical path of infrared ray (incident light) 29formed by fixed mirror 31 and movable mirror 32 which is made movable bymeans of moving apparatus 33, to be incident on plume 15. The infraredray (transmitted light) 34 which has transmitted through plume 15 passesthrough outlet window 36 by means of fixed mirror 31 and movable mirror32, and enters time division Fourier transform infrared spectroscope 35.By analyzing the information obtained by infrared spectrometer 35 byanalyzing apparatus 25, types and ratio and molecule seeds playingimportant role in forming the thin film and having absorption band inthe infrared range at various portions of the plume 15 can berecognized. By controlling parameters for film formation by using thecontrol apparatus 27 based on the result of analysis obtained fromanalyzing apparatus 26, the state of the plume 15 can be kept constant.Therefore, a film of high quality having uniform composition and smallerdeposition or proper orientation can be formed.

A seventy-second embodiment of the present invention will be describedwith reference to FIG. 114. The apparatus of this embodiment includes,referring to FIG. 114, an analyzing apparatus 26 for analyzing massspectrum, a controlling apparatus 27 which is the same as controllingapparatus 27 shown in FIG. 112, and a mass spectrometer 37 for measuringions generated from the vicinity of substrate 2.

The operation is as follows. In the thin film forming apparatus usinglaser structured as described above, ions in the plume emitted from thevicinity of substrate 2 are measured by mass spectrometer 37. Byanalyzing the measured information by analyzing apparatus 26, types,energies and ratio of ions playing important roles in forming the thinfilm such as metal ions, oxide ions, cluster ions and the like can berecognized. Based on the result of analysis obtained from analyzingapparatus 26, by controlling parameters for film formation by usingcontrolling apparatus 27, the state of plume 15 can be kept constant.Therefore, a film of high quality having uniform composition and lessimpurities or superior orientation can be formed.

A seventy-third embodiment of the present invention will be describedwith reference to FIG. 115. The basic structure of the apparatus shownin FIG. 115 is approximately the same as that of FIG. 148 except thatcontrolling apparatus 13 is not provided.

The operation will be described. The basic mechanism for film formationis the same as in the prior art example. Laser beam 16 emitted fromlaser unit 10 is condensed by condenser lens 9 and passed through laserinlet window 7 of chamber 1 to be incident on raw material target 5placed on turntable 11 in chamber 1. Substrate holder 3 is positionedinclined by a prescribed angle from the central axis of the generatedplume 15. The central axis thereof passes in front of the center ofsubstrate 2. Therefore, excited atoms and ions included in a widesection on the side of the plume 15 reaches substrate 2 and aredeposited thereon to form a thin film. In order to make uniform the filmthickness, the thin film is formed while the substrate holder 3 isrotated.

As described above, in accordance with this invention, parallel movementis not necessary during film formation, and therefore controllingapparatus 13 can be dispensed with. Accordingly, a thin film havinguniform thickness can be formed over a large area relatively easily.

A seventy-fourth embodiment of the present invention will be describedwith reference to FIG. 116. Referring to FIG. 116, in this embodiment,when target is irradiated with laser, a plume is generated from thesurface of the target. Since the target and the substrate are botherected vertical to the ground, all the generated foreign matters falldownward. Therefore, foreign matters are not deposited on the substratesurface. Substrate holder 3 is rotatable by a rotary mechanism 260,allowing film formation to uniform film thickness. By dividing thetarget into left and right two and by rotating target holder 11,multiple targets can be provided. There is provided an oxygen inlet onthe side of laser beam inlet window 7, and by introducing oxygen gas,frost on the inlet window can be prevented. By closing shutter 261,atoms reaching the surface of the substrate can be controlled, and hencestart and end of film formation can be controlled.

As described above, according to this embodiment, the substrate surfaceis not contaminated by foreign matters, a film having uniform thicknessand uniform quality can be formed, and therefore a thin film formingapparatus using laser allowing formation of superior filmcharacteristics than in the prior art can be obtained.

A seventy-fifth embodiment of the present invention will be describedwith reference to FIG. 117. FIG. 117 is a schematic diagram showing thethin film forming apparatus using laser in accordance with oneembodiment of the present invention. In the figure, the same referencecharacters as in the prior art shown in FIG. 148 denote the same orcorresponding portions.

The operation will be described. The laser beam 16 emitted from laserunit 10 is condensed by condenser lens 9 and passed through laser inletwindow 7 of chamber 1 to be incident on raw material target 5 placed onturntable 11 in chamber 1. Consequently, a plume is generated and thethin film is formed on substrate 2, through the same steps as in theprior art example. However, different from the prior art, in thisembodiment, the point of focus 133 of laser beam 13 is set deeper thanthe surface of target 5. By such a structure, laser beam is not focusedin chamber 1, so that breakdown of the introduced gas such as oxygendoes not occur at the point of focus. Therefore, the thin film is notdamaged by undesirable ions or the like. This enables formation of athin film having higher quality than in the prior art.

A seventy-sixth embodiment of the present invention will be describedwith reference to FIG. 118. The apparatus of this embodiment includes,referring to FIG. 118, a laser unit 128 having laser beam of longerwavelength than laser unit 10, and a condenser lens 127.

The operation is as follows. The process for forming a thin is the sameas the prior art. However, during thin film formation, laser beam 128 isdirected to the surface of target 5 by using lens 127, from laser unit126. The wavelength of laser beam 128 is sufficiently long to preventevaporation of the material from the target surface, and its intensityis weak enough to prevent evaporation of the material from the targetsurface. However, it is adapted such that the target surface is set tomelted state or immediately below the melting point. Since the targetsurface is such a condition, at the time of laser abrasion of thesurface of target 5, the surface is not made rough. This preventsgeneration of foreign matters on the surface of substrate 2. Laser beam128 may be applied continuously, or it may be applied in the shape ofpulses. This laser beam may be or may not be in synchronization withlaser beam 16. The surface roughness of the target causes unevenirradiation of laser beam 16 and causes scatters of drops from thetarget. Such drops may cause foreign matters on the surface of substrate2.

A seventy-seventh embodiment of the present invention will be describedwith reference to FIG. 119. This embodiment includes, referring to FIG.119, a main film forming chamber 263, a load lock chamber 264, apreliminary film forming chamber 265, platinum (Pt) target 266, atitanium (Ti) target 267, a target 268 including copper oxide (PbO) andPbTiO₃ divided and juxtaposed in two lines, and a conveyer system 269.

The operation is as follows.

In the preliminary film forming chamber, an underlying film of metal (Ptor the like) is formed by laser sputtering. Then, in the preliminaryfilm forming chamber, Ti film is formed. Thereafter, the substrate ismoved to the main film forming chamber in vacuum by using conveyingsystem 269. Then, in the main film forming chamber, PbO film is formedby sputtering in oxygen (O₂) atmosphere. At this time, Ti and PbO atabout 500 to about 600° C. react with each other, forming a PbTiO₃perovskite layer at a low temperature as an underlayer. Since titaniumoxide (TiO₂) is formed at the lower most layer, good adhesion with theunderlayer is provided. After the formation of the underlying perovskitelayer, by sputtering the target portion of PbTiO₃, a film havingsuperior crystal properties can be formed at a low temperature. WhenPbTiO₃ is to be sputtered from the start, the substrate temperature mustbe increased to about 700° C. or higher, since various crystal layersare unavoidably formed at a low temperature. Finally, annealing iscarried out in O₂ N₂ O or O₃ atmosphere in the sputtering chamber. Tothis step, the substrate can be moved without exposure to the atmosphereat all. Therefore, film can be formed with less introduction ofimpurities, and the perovskite layer can be formed stably at a lowtemperature.

Though the film is formed by sputtering PbO in oxygen atmosphere in theabove described embodiment, it is not limited thereto. A TiO₂ film maybe temporarily formed by carrying out annealing at 500° C. to 800° C. inoxygen atmosphere after formation of Ti, and by sputtering PbO, acrystal of PbTiO₃ can be obtained.

Though PbTiO₃ is formed as the sputter target on the underlying crystalof PbTiO₃ in the above described embodiment, it is not limited thereto.Two targets of PbO and TiO₂ may be sputtered and by applying mixture tothe substrate, a thin film of PbTiO₃ may be formed.

At the time of sputtering Ti in the preliminary film forming chamber,when nitrogen (N₂) atmosphere is used, titanium nitride is formed on Pt.This serves as a barrier layer for preventing diffusion of Pt intoPbTiO₃ during film formation, annealing and, in addition, heating of thesubstrate in the subsequent steps, so that it is effective to reduceleak current or the like.

As described above, in this embodiment, since the first oxide film isformed in oxygen atmosphere after the formation of an underlying metalfilm, a underlaying crystal of high quality can be formed at a lowtemperature, and therefore a thin film forming apparatus using laserallowing formation of a thin film having superior film characteristicthan in the prior art can be obtained.

A seventy-eighth embodiment of the present invention will be describedwith reference to FIG. 120. This embodiment was made to solve theproblem of degraded function of the thin film among the above describedproblems of the prior art. Its object is to provide a thin film formingapparatus using laser for forming a thin film of high quality byconnecting a plurality of film chambers.

In order to make clear the feature of this embodiment, the problem ofthe conventional thin film forming apparatus using laser will bedescribed in greater detail. In the conventional film forming apparatususing laser, even when a number of thin films are to be formed, filmformation is done in one chamber. If thin films which act to degradecharacteristics of each other when mixed are formed in one chamber, thecharacteristics of the resulting thin films are naturally not so good.For example, assume that a silicon is formed on the substrate and thengallium arsenide is formed thereon. An operation of silicon used forforming the silicon thin film existing the chamber at a certain vaporpressure. Therefore, during formation of gallium arsenide, the vapor ofsilicon is mixed in the thin film of gallium arsenide. Since siliconserves as dopant to gallium arsenide, this much affects thecharacteristics of the gallium arsenide, even if the amount of siliconis very small. Accordingly, it is difficult to form a number of thinfilms of such combination as silicon and gallium arsenide. In view ofthis, in this embodiment, a plurality of chambers are connected.

Referring to FIG. 120, the thin film forming apparatus using laser ofthis embodiment includes a gate valve 119, a chamber 120 having afunction of forming a thin film, a partial reflection mirror 121provided for directing the laser beam to respective chambers, and achamber 122.

The operation will be described. The process for forming the thin filmis the same as in the prior art. First, a substrate is placed in chamber120, and a thin film 123 is formed. Then, the substrate is moved tochamber 122. At this time, since chambers 122 and 120 are connected toeach other with a gate valve 119 interposed, the substrate is notexposed to the atmosphere during movement. When the substrate is movedto chamber 122, a thin film 124 which is not compatible with thin film123 is formed. Since chambers 120 and 122 are partitioned by gate valve119, the vapor existing in chamber 120 do not enter chamber 122, andtherefore a thin film 124 of high quality can be formed. Since thesubstrate is not exposed to the atmosphere when it is transferredbetween chambers 120 and 122, the film quality is not degraded by oxygenentering the interface between thin films 123 and 124. Gate valve 119 ofthis embodiment may be replaced by an O ring. Though the O ring has suchdisadvantages that it cannot be used under high vacuum and that it isweak against heat, it is inexpensive and convenient for use.

A seventy-ninth embodiment of the present invention will be describedwith reference to FIG. 121. In the thin film forming apparatus usinglaser of this embodiment, a plurality of film forming chambers areconnected with a plurality of gate valves interposed, and by using asample conveying mechanism, a number of thin films are formed andprocessed.

In the conventional apparatus, when thin films of different groups, suchas superconductive films requiring much oxygen and semiconductor filmsnot requiring oxygen are to be vapor-deposited on the same substrate, itis necessary to form the film by taking the substrate once to theatmosphere and put the substrate to a different chamber. In thisembodiment, the chambers are connected by using gate valve, thin filmsof high quality can be formed without exposing these to the atmosphere,and the process can be carried out at high efficiency. When a number oftargets are used to form a number of thin films in the same chamber,foreign matters are inevitably mixed. However, since the chambers aredivided as described above for materials to which entrance of foreignmatters are highly undesirable, thin films of superior quality can beformed. The thin film forming apparatus using laser in accordance withthe present invention includes, in addition to the basic structure whichis approximately the same as the prior art example of FIG. 148, areflection mirror 100, a gate valve 101 and a sample conveyer mechanism102.

The operation is as follows. The mechanism for film formation isbasically the same as the prior art. Laser beam 16 emitted from laserunit 10 is condensed by condenser lens 9 and passed through laser inletwindow 7 of chamber 1 to be incident on raw material target 5 placed onturntable 11 in chamber 1. Excited atoms and ions included in plume 15reach the substrate 2 and are deposited thereon to form a thin film. Inorder to make uniform the film thickness, substrate holder 3 is rotatedwhile the thin is formed. When one thin film is formed, the sample forthin film formation is moved to the next film forming chamber 1 by usingsample conveying mechanism 102, and film formation using laser iscarried out in the similar manner. For improving efficiency, metal filmsand insulating films are formed by using a deposition apparatus or thelike other than the film forming apparatus using laser.

As described above, in accordance with this embodiment, entrance offoreign matters into the film forming sample can be avoided, laminatedfilms can be formed without exposing the sample to the atmosphere, andthe efficiency in thin film formation can be improved.

An eightieth embodiment of the present invention and its modificationwill be described with reference to FIGS. 122 and 123. The embodimentwas made to solve the problem of degraded function of the thin filmamong the problems of the prior art. Its object is to provide a thinfilm forming apparatus using laser in which degradation of the thin filmproperties can be prevented by directing the laser beam reflected fromthe target again to the target.

In order to make clear the features of this embodiment, the problem ofthe thin film forming apparatus using laser of the prior art will bediscussed in greater detail. In the conventional thin film formingapparatus using laser, the laser beam is directed to the target onlyonce. Since the target has some reflectance with respect to the laserbeam, part of the laser which has been impinged on the target isreflected and goes away from the target. The laser beam reflected fromthe target impinges on the chamber or the substrate. This reflected beammay evaporate impurities deposited on the chamber, or it may change thecharacteristics of the thin film formed on the substrate, causingdegraded function of the thin film. The thin film forming apparatususing laser in accordance with the present embodiment is basically thesame as the prior art example shown in FIG. 148 except that a target 17having the shape of a crucible such as shown in FIG. 122 is used.

The operation is as follows. The process for forming a thin film is thesame as in the prior art. In the prior art, laser beam 16 is directed tothe target 5 and reflected therefrom, to be directed to the chamber, thesubstrate or the like. In this embodiment, the target has a shape of acrucible. The laser beam is directed to the inside of this crucibleshaped target 117. Consequently, the laser beam incident and reflectedfrom the wall of target 117 is again directed to target 117, andevaporates the target material. The evaporated target material generatesa plume, which forms a thin film on substrate. laser beam 16 isrepeatedly reflected and goes out from the bottom of crucible, returnsto the upper part of crucible, and then goes out of the crucible shapedtarget 117. The laser beam may done be directed to the chamber orsubstrate, causing some degradation of the thin film function. However,since the laser beam is repeatedly reflected in the crucible, the beamwhen going out of the crucible, has low intensity. Therefore, suchadverse effect of the beam may be negligible. For example, let us assumethat the reflectance of the target with respect to the laser beam is50%. In the prior art example, the laser beam which is reflected fromthe target and directed to the chamber or the substrate has half theintensity of the original beam. In this embodiment, the laser beam isreflected a number of times in the crucible and goes out from thecrucible. Assuming that the laser beam is reflected ten times in thetarget, the intensity of the laser beam would be ten times 0.5, which is0.1%. This is 1/500 of the prior art example, and since it is so small,it can be neglected.

A modification of this embodiment will be described. The process forforming the thin film in this embodiment is the same as the prior art,and the function of this embodiment is the same as the embodiment above.Referring to FIG. 123, in this modification, laser beam is directed totwo opposing targets 118, and therefore laser beam will be incident onthe upper and lower targets alternately. Consequently, the intensity ofthe laser beam going out from the target has its intensity made veryweak, and therefore it does not degrade the function of the finishedthin film. Since the laser beam impinges on the target a number oftimes, the amount of plume is increased, and hence the rate of thin filmformation can be improved.

As described above, in accordance with this embodiment, the laser beamreflected from the target is again directed to the target. Therefore,the laser beam is not directed to the chamber or the substrate, so thatthe thin film can be formed with its function not degraded.

An eighty-first embodiment of the present invention will be describedwith reference to FIG. 124. FIG. 124 is a schematic diagram showing thethin film forming apparatus using laser in accordance with oneembodiment of the present invention. In the figure, the same referencecharacters as in the prior art example shown in FIGS. 148 and 149 denotethe same or corresponding portions, and description thereof will not berepeated.

The apparatus of this embodiment includes, referring to FIG. 124, anionizing chamber 311 placed between target 5 and substrate 2, in which ahot cathode 312 emitting thermoelectrons and an anode 313 are placedspaced apart by a prescribed distance. The apparatus of this embodimentfurther includes an insulator 314 for electrically insulating thesubstrate holder 3 and vacuum chamber 1, and a DC power source 315connected to the substrate holder.

The operation is as follows. When target surface 5 is irradiated bylaser beam 16, a high density plasma is locally generated at theirradiated portion, generating a plume 15 which is like a flame of acandle toward substrate 2. Excited neutral particles, electrons-ions inthe form of atoms, molecules or clusters constituting the target existin the plume. When these particles pass through ionizing chamber 311placed between the target and the substrate, neutral particles in theplume are ionized by accelerated electron beams emitted from hot cathode312 and proceeding straight to anode 313. Thus, after passage throughionizing chamber, ion beams consisting of the target material are formedand directed to the substrate. Since the substrate holder iselectrically insulated from the vacuum chamber by means of insulator 314and is connected to DC power source 315, potential can be freely appliedto the substrate holder, that is, to the surface of the substrate. Whena negative potential is applied to the substrate, ion beams of thetarget material generated by the ionizing chamber can be acceleratedtoward the substrate, enhancing kinetic energy at the time ofirradiation of the substrate.

In the conventional apparatus, crystallization of the thin film ispromoted by increasing the substrate temperature when a thin film is tobe formed on the substrate. In this embodiment, kinetic energy can beapplied to the particles of the material of the thin film, and byappropriately selecting the value of the kinetic energy, the substratetemperature necessary for crystallizing the thin film can be decreasedwithout any damage to the substrate.

Though the neutral particles in the plume are ionized by electron beamsin this embodiment, these particles may be ionized by optical function,for example by directing a second laser beam, a vacuum ultraviolet lampor SR light to the plume between the target and the substrate, toprovide similar effect.

An eighty-second embodiment of this invention will be described withreference to FIG. 125. The basic structure of FIG. 125 is similar tothat of FIG. 149. In this embodiment, referring to FIG. 125, the laserbeam 16 emitted from laser 10 is condensed by condenser lens 9 andpassed through laser inlet window 7 of chamber 1 to be incident on rawmaterial target 5 placed on turntable 11 in chamber 1. To plume 15generated by this irradiation, hydrogen radicals and hydrogen ions 105are directed from a hydrogen radical source and hydrogen ion source 103.Electron beam 107 is emitted from electron gun 106. Consequently, groupsof atoms can be removed or dissolved, and therefore steep interfacestructure of a very thin laminated layer can be formed. Ions included inthe plume are changed to neutral atoms and particles. Substrate 2 isplaced fixed on substrate holder 3, opposing to material target 5, andthus excited atoms and neutral atoms in plume 15 reach substrate 2 andare deposited thereon to form a thin film.

An eighty-third embodiment of this invention will be described withreference to FIG. 126. In the figure, the same reference characters asin FIGS. 148 and 149 denote the same or corresponding portions.

The operation is as follows. Laser beam 16 emitted from laser unit 10 iscondensed by condenser lens 9 and passed through laser inlet window 7 ofchamber 1 to be incident on raw material target 5 placed on turntable 11in chamber 1. At the portion of raw material target 5 which isirradiated with laser beam, a plasma of the target material is generatedabruptly at the time of laser irradiation, and in the process of coolingthe plasma in several ten ns, isolated excited atoms, molecules and ionsare generated. These groups of excited atoms, molecules and ions havelives of several microseconds, and they are emitted in the space to forma plume 15 which is like a flame of a candle.

Meanwhile, substrate 2 is placed fixed on substrate holder 3, opposingto raw material target 5. Excited atoms, molecules and ions and thetarget material in the form of clusters in which these atoms and ionsand the like are combined in plume 15 reach the substrate 2, and aredeposited and crystallized to form a thin film, in the similar manner asin the prior art.

Here, power is supplied to an electromagnetic coil 309 from a powersource 311 for the electromagnetic coil and a magnetic field havingmagnetic lines of force 310 and the intensity of up to 1 kG is appliedto and near raw material target 5, movement of charge particles such asions and electrons in plume 15 are influenced by the magnetic field andthese charged particles drift in the direction of the magnetic lines offorce 310. Therefore, when the magnetic field is formed such that themagnetic lines of force 310 are parallel to the surface of target 5 andnot passing through the surface of substrate 2, ions in plume 15 do notreach substrate 2, suppressing impingement and deposition of ions on thesurface of substrate 2. Meanwhile, non-charged particles such as neutralatoms, molecules and clusters in plume 15 are not influenced by themagnetic field so that they reach and are deposited on the surface ofsubstrate 2 as in the prior art. Therefore, a thin film of high quality,in which the problem of degradation of the substrate and degradedfunctions of the thin film caused by undesirable side reaction derivedfrom impingement and deposition of ions are eliminated, can be obtained.

At the initial stage of irradiation of raw material target 5 with laserbeam 16, that is, at the initial stage of deposition and thin filmformation of target material on substrate surface 2, preferable effectscan be often obtained with respect to the quality of the completed filmif ions in plume 15 reach the surface of the substrate 2. This isbecause the ions excite, in non-equilibrium, the state of electrons ofimpurity particles deposited on the surface of substrate 2 for atoms andmolecules constituting the impurity thin film formed on the surface,which leads to removal and separation of the impurity particles orimpurity thin film from the surface of substrate 2. Thus clear substratesurface is exposed at the initial stage of film formation on the surfaceof substrate 2, using the target material, and initial nucleus of thethin film of the target material can be generated at a pure state on thesurface of the substrate 2 without impurities. Consequently, crystal ofthe thin film of the target material grows regularly, enabling formationof a thin film of high quality in a clean condition, relatively freefrom the problem of the impurities at the interface. Therefore, in sucha case, in the initial stage of irradiation of raw material target 5with laser beam 16, that is, in the initial stage of deposition and thinfilm formation of target material on the surface of substrate 2, theswitch of power source 311 for supplying power to electromagnetic coil309 should be turned off so that there is not a magnetic fieldgenerated. In the later step of film formation, power source 311 isturned on to supply power to electromagnetic coil 309, whereby amagnetic field having the magnetic lines of force 310 and having theintensity of up to about 1 kG is applied to and near target 5,suppressing impingement of ions in plume 15 to substrate 2.

In order to suppress impingement and deposition of ions on the surfaceof substrate 2 by preventing ions in plume 15 from reaching substrate 2,conventionally, a metal mesh is placed parallel to the surface ofsubstrate 2 in the vicinity of substrate 2 and a negative potential isapplied to the metal mesh, so that ions are trapped by the mesh.However, in that case, metal impurities are emitted due to mutualfunction of the mesh and the ions in the plume 15. Passage of non-chargeparticles such as neutral atoms and molecules as well as clusters inplume 15 is suppressed by the mesh, causing metal contamination of thethin film and lower rate of thin film deposition. By contrast, in thepresent embodiment employing magnetic field, such problems of metalcontamination and lower rate of thin film deposition can be solved.

A heater 4 for heating the substrate is provided in substrate holder 3,and therefore, post annealing in which a film deposited at a lowtemperature is annealed at a temperature higher than the crystallizingtemperature to form a thin film of superior quality, and as-depositionin which substrate itself is kept at a temperature higher than thetemperature for crystallization at the time of deposition so that acrystallized thin film is formed at the site can be carried out. In theas-deposition method, active oxygen atmosphere is used as well, and, anozzle 6 for supplying gas 19 containing oxygen during formation of anoxide thin film is provided as shown in the figure for example, so thatoxygen atmosphere is provided near substrate 2 so as to promotegeneration of oxide on substrate 2, as in the prior art example.

An eighty-fourth embodiment of the present invention will be describedwith reference to FIG. 127. In the figure, the same reference charactersas in FIG. 126 denote the same or corresponding portions.

This embodiment is adapted such that a magnetic field having magneticlines of force 310 and intensity of up to about 1 kG or higher caused byelectromagnetic coil 309 extend vertical to the surface of raw materialtarget 5 and expanding toward the surface of substrate 2. Movement ofcharged particles such as ions and electrons in plume 15 are influencedby the magnetic field formed at target 5 and substrate 2 as well as inthe vicinity thereof, so that the charged particles drift in thedirection of the magnetic lines of force 310. Therefore, if the magneticlines of force 310 is formed vertical to the surface of target 5 andexpanding toward the surface of substrate 2, ion flux in plume 15decreased toward substrate 2, suppressing impingement and deposition ofions on the surface of substrate 2. Meanwhile, non-charged particlessuch as neutral atoms, molecules and clusters and the like in plume 15are not influenced by the magnetic field, so that they impinge and aredeposited on the surface of substrate 2 as in the prior art. Therefore,a thin film of high quality can be formed in which degradation of thesubstrate and degradation of thin film function caused by undesirableside reaction derived from impingement•deposition of ions can beeliminated.

In the eighty-third and eighty-fourth embodiments described above,magnetic field is applied by using electromagnetic coils. However, apermanent magnet may be used instead of the electromagnetic coil, toprovide the same effect. If a permanent magnet is used, power supply forsupplying power necessary for electromagnetic coils can be dispensed of,making compact the whole apparatus. However, the effects obtained byturning on/off the magnetic field so as to control movement of chargedparticles such as ions and electrons in the plume cannot be expected.

An eighty-fifth embodiment of the present invention will be describedwith reference to FIGS. 128 and 129. FIG. 128 is a schematic diagramshowing the thin film forming apparatus using laser in accordance withone embodiment of the present invention, and FIG. 129 is an illustrationshowing movement of charged particles in the plume near the surface ofthe target. In these figures, the same reference characters as in theprior art example of FIGS. 148 and 149 denote the same or correspondingportions, and description thereof will not be repeated.

Referring to FIGS. 128 and 129, the apparatus of this embodimentincludes a ring-shaped permanent magnet provided along target 5, whichgenerates magnetic field parallel to the surface of target 5, near thesurface of target 5.

The operation is as follows. When the target surface is irradiated withlaser beam 16, a high density plasma is generated locally at theirradiated portion, generating a plume 15 which is like a flame of acandle toward substrate 2. Excited neutral particles in the form ofatoms, molecules or clusters constituting the target as well aselectrons and ions exist in the plume. Since there is a magnetic fieldparallel to the target surface, near the target surface, electrons andions in the plume emitted from the target move spirally along themagnetic lines of force as shown in FIG. 129. At this time, radius ofrotation of the electrons and ions at this time are determined by thespeed of the particles when they exit the target and by the intensity ofthe applied magnetic field. Thus, by selecting an appropriate intensityof the magnetic field, the loci of the electrons and ions emitted fromthe target can be bent significantly so as to prevent these chargedparticles from reaching the surface of the substrate. Meanwhile, neutralparticles in the plume are transmitted to the substrate withoutinfluenced by the magnetic field, so that they are adhered and depositedon the surface of the substrate, forming a thin film. Thus, damage tothe substrate caused by electrons and ions reaching the substrate can beprevented.

In the conventional apparatus, in order to prevent charged particles inthe plume from reaching the substrate, front surface of the substrate iscovered by a grid electrode, and electric field is put in the plume soas to repel electrons and ions to the target so that the electrons andions can be prevented from reaching the substrate. However, in thismethod, the electrode is directly in contact with the plume so that thesurface of the electrode is sputtered by ion impingement. Therefore,there is a problem of contamination of the substrate by the material ofthe electrode. In this embodiment, the movement of charged particles iscontrolled by a magnetic field and the plume does not touch any metalsuch as an electrode. Therefore, this problem of contamination can beprevented.

Though a ring-shaped permanent magnet is provided around the target,what is important is to generate a magnetic field parallel to thesurface of the target, and therefore various shapes and methods ofproviding the permanent magnet are possible. The same effect can beexpected when a magnetic coil is used.

As described above, in accordance with this embodiment, since a magneticfield parallel to the surface of the target is generated, chargedparticles in the plume generated by laser beam irradiation of the targetsurface have their loci bent, so that these particles are prevented fromreaching the substrate. Thus a thin film can be formed over thesubstrate surface by using excited neutral particles in the plume only,which allows formation of a thin film of high quality without anydamage.

An eighty-sixth embodiment of this invention will be described withreference to FIG. 130. FIG. 130 is a schematic diagram showing the thinfilm forming apparatus using laser in accordance with one embodiment ofthe present invention. In the figure, the same reference characters asin the prior art example of FIGS. 148 and 149 denote the same orcorresponding portions, and description thereof will not be repeated.

Referring to FIG. 130, the apparatus of this embodiment includes a setof magnetic coils 316 and 317 provided around a vacuum chamber 1, whichare respectively connected to independent coil power supplies 318 and319 feeding current.

The operation is as follows. When the target surface is irradiated withlaser beam 16, a high density plasma is generated locally at theirradiated portion, generating a plume 15, which is like a flame of acandle toward substrate 2. Excited neutral particles in the form ofatoms, molecules or clusters as well as electrons and ions constitutingthe target exist in the plume. These particles reach the substratesurface and are adhered and deposited on the surface to form a thinfilm. The direction of scattering of the particles emitted from thetarget surface tends to be approximately vertical to the target surface.Therefore, the extent of the plume reaching the substrate surface isvery small compared with the area of the substrate having the diameterof about 6 to 8 inches used in the semiconductor industry. Therefore, inthis embodiment, to a set of magnetic coils juxtaposed with anappropriate space, currents of opposite directions are applied by twocoil power supplies connected thereto. Consequently, a cusp magneticfield having such a distribution of magnetic lines of force as shown inFIG. 130, in the space between the target and the substrate by thesemagnetic coils. The electrons and ions in the plume emitted from thetarget move spirally along the magnetic lines of force, so as to expandalong the magnetic lines of force. Thus the plume mentioned above can beexpanded in the radial direction by the function of the cusp magneticfield, and therefore a thin film can be formed uniform in the radialdirection of a substrate having larger diameter, by a single plume.

Though the cusp magnetic field is generated by providing a set ofmagnetic coils around the vacuum container in this embodiment, what isimportant is to generate a cusp magnetic field in the space between thetarget and the substrate. Therefore, similar cusp magnetic field can begenerated by providing a magnetic coil or a permanent magnet in thevacuum container to provide the same effect.

An eighty-seventh embodiment of this invention will be described withreference to FIGS. 131 and 132. In this embodiment, an apparatus forforming a thin film of high quality in which, when a thin film is formedby deposition on a substrate placed opposing to the target by laser beamirradiation of the target, the substrate is moved so that a portion onwhich the thin film is mainly deposited of the substrate is changed,characterized in that a shielding plate for shielding a portion of theplume is provided between the target and the substrate, is provided.

The main feature of this embodiment is that it includes a shieldingplate for partially shielding the plume between the target and thesubstrate, when a film is formed by moving the substrate in the filmforming chamber so that the portion on which the thin film is mainlydeposited on the substrate is changed. At a position of the target whichis irradiated with the laser beam, a plasma which is called a plumewhich is a collection of active particles for forming thin film isgenerated. The plume is generally constituted by excited atoms, ions andclusters having the same composition as the target. The particlesconstituting the plume have spatial distribution of the same compositionratio as the target near the target immediately after the generation ofthe plume. However, by the time it reaches the substrate after diffusionin the chamber, spatial distribution of the particles constituting theplume changes due to the difference of diffusion coefficients of theparticles. More specifically, the density distribution of heavierparticles comes to be higher at the central portion of the plume, anddistribution density of lighter particles comes to be higher atperipheral portions. Therefore, difference of distribution of the filmquality of the thin film deposited on the substrate becomes significant,making it difficult to form a thin film of uniform quality over a largearea. In this embodiment, a plume shielding plate having an opening atthe center is provided between the target and the substrate, so thatonly the central portion of the plume is directed to the substrate. Thusdifference in spatial distribution of the density of particlesconstituting the plume in contact with the substrate can be reduced.

It is known that ions in the plume degrade the quality of the thin filmdeposited on the surface of the substrate. Therefore, by applyingpositive or negative potential with respect to the target to the plumeshielding plate having the opening so as to prevent ions from reachingthe substrate, the quality of the deposited thin film can be improved.

FIG. 131 is a schematic diagram of one example of the thin film formingapparatus using laser in accordance with this embodiment. In the thinfilm forming apparatus using laser shown in FIG. 131, laser beam 16emitted from laser unit 10 and passed through condenser lens 9 entersthe laser inlet window 7 of chamber 1 to be incident on raw materialtarget 5 placed on turntable 11 of chamber 1. Turntable 11 can berotated at an arbitrary rate of rotation by means of motor 14. Chamber 1can be evacuated to a high vacuum. Substrate 2 is placed opposing totarget 5, and a plume shielding plate 4814 is placed between thesubstrate 2 and target 5. Plume shielding plate 4814 has an opening of10 mm in diameter at the center. Positions of substrate 2 and plumeshielding plate 4814 may be changed in synchronization with the pulsefrequency of the laser beam.

By using the thin film forming apparatus using laser described above, aY₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thin film was fabricated inaccordance with the method of the present invention. An SrTiO₃ singlecrystal substrate was used as substrate 2, and a substrate temperaturewas set to 700° C. A Y₁ Ba₂ Cu₃ O_(7-x) sintered body having thediameter of 2 cm was used as target 5. The distance between the centerof substrate 2 and the position of laser beam irradiation of target 5was set to 5 cm. The inside of chamber 1 was evacuated to 1×10⁻⁴ Torr,and then oxygen gas is introduced to 200 m Torr.

An excimer laser having the wavelength of 193 nm was used, the laseroutput was set to 3 J/cm², the area of laser beam irradiation was set to2×3.5 mm², and the pulse frequency was 2 Hz. The target was rotated at120 rpm.

Film formation was carried out for 35 minutes under the abode describedconditions, and variation in film thickness distribution andsuperconductive characteristics of the obtained oxide superconductivethin film were measured. Consequently, variation of film thicknessdistribution of the oxide superconductive thin film fabricated inaccordance with the method of the present invention was ±10% in a circlehaving the diameter of 20 mm, and the critical temperature was 93 K.Meanwhile, the variation of film thickness distribution formed under thesame conditions except that the plume shielding plate is removed was±10% in a circle having the diameter of 20 mm, and the criticaltemperature was 88 K. The average film thickness of the oxidesuperconductive thin film formed in accordance with the presentinvention was 3000 Å.

FIG. 132 is a schematic diagram of one modification of the thin filmforming apparatus using laser of this embodiment. In the thin filmforming apparatus using laser shown in FIG. 132, laser beam 16 emittedfrom laser unit 10 and passed through condenser lens 9 enters laserinlet window 9 of chamber 1 to be incident on raw material target 5placed on turntable 11 of chamber 1. Turntable 11 can be rotated at anarbitrary rate of rotation by means of motor 14. Chamber 1 can beevacuated to a high vacuum. Substrate 2 is placed opposing to a target5, and a plume shielding plate 4814b is positioned between the substrate2 and target 5. Plume shielding plate 4814b has an opening of 10 mm indiameter at the central portion thereof. A potential of +100V is appliedto the target. Substrate 2 can be moved in synchronization with pulsefrequency of the laser beam.

By using the thin film forming apparatus using laser described above, aY₁ Ba₂ Cu₃ O_(7-x) oxide superconductive thin film was fabricated inaccordance with the method of the present invention. SrTiO₃ singlecrystal substrate was used as the substrate 2, and the substratetemperature was set to 700° C. A sintered body of Y₁ Ba₂ Cu₃ O_(7-x) ofthe diameter of 2 cm was used as target 5. The distance between thecenter of substrate 2 and the point of laser beam irradiation of thetarget was set to 5 cm. The inside of chamber 1 was evacuated to 1×10⁻⁴Torr, and then oxygen gas was introduced to 200 m Torr.

An excimer laser having the wavelength of 193 nm was used as the laser,the laser output was set to 3 J/cm², the area of laser beam irradiationwas set to 2×3.5 mm², and the pulse frequency was set to 2 Hz. Thetarget was rotated at 120 rpm.

Film formation was carried out for 35 minutes under the above describedconditions, and film thickness distribution and superconductivecharacteristics of the obtained oxide superconductive thin film weremeasured. Consequently, variation in film thickness distribution of thesuperconductive thin film fabricated in accordance with the method ofthe present invention was ±10% in a circle having the diameter of 20 mm,and the critical temperature was 93 K. Meanwhile, variation of filmthickness distribution of a film formed under the same condition withthe plume shielding plate removed was ±10% in a circle having thediameter of 20 mm, and the critical temperature was 88 K. Average filmthickness of the oxide superconductive thin film fabricated inaccordance with the method of the present invention was about 3000 Å.

An eighty-eighth embodiment of the present invention will be describedwith reference to FIG. 133. Referring to FIG. 133, the apparatus of thisembodiment includes an atom trapper 285 having a through hole 286through which laser beam 16 passes and a heater 287. In the figure, thesame reference characters as in FIG. 148 denote the same orcorresponding portions.

The operation will be described. When a film is formed on substrate 2 byirradiating opposing target 5 with laser beam 16, a plume 15 isgenerated. However, atoms emitted at an angle not reaching the wafer 2inherently are adhered and deposited on the surface of the trapper. Atthis time, since the trapper 285 is placed near the point of generationof plume 15, the time of free flight of the atoms is short. Therefore,the possibility of the atoms in the plume 15 being combined in the gasphase to be particles is very low. Further, since trapper 285 is heatedby means of a heater, deposited atoms are turned to a stable smooth film288. At this time, a material having the same coefficient of linearexpansion as the material of target 5 should be selected as the materialof trapper 285, in order to prevent separation of the deposited film.

When film forming process is carried out continuously and a filmexceeding some thickness is deposited on trapper 285, it can be takenout for cleaning and used again.

In accordance with this embodiment, generation of gas in the reactionchamber can be suppressed, and therefore a thin film forming apparatususing laser allowing continuous thin film formation with the filmshaving less particle defects can be obtained.

An eighty-ninth embodiment of the present invention will be describedwith reference to FIGS. 134A to 140. The present embodiment is to solvethe following problems of the above described embodiment.

Generally, when external atmosphere is introduced to the film formingapparatus, the quality of the film is degraded, and therefore variousmeans are taken to keep clean the inside of the apparatus. However, in afilm forming apparatus using laser beam, a window 7 provided at chamber1 for introducing the beam is frosted by materials scattered from target5, so that the intensity of the laser beam reaching target 5 decreases.Therefore, it becomes necessary to change the window periodically.

The apparatus of this embodiment eliminating such a conventional problemincludes, typically, a number of apertures 4230 having such a shape asshown in FIG. 134B provided between the window 7 and the sidewall ofchamber 1 as shown in FIG. 134A.

The operation is as follows. When target 5 provided in chamber 1 isirradiated with laser beam 16, molecules constituting the target areevaporated, generating a plume 15 which is like a flame of a candle. Atthat time, part of the materials scattered from target 5 are turned todust. The dust may be deposited on the window 7 provided for introducinglaser beam 16 into chamber 1. Therefore, a plurality of apertures 4230are positioned between the window and target 5 so that solid angle ofthe window viewed from the target 5 is made smaller. At this time, it ismore effective to make the value of solid angle Ω=S/L smaller, where Srepresents the size of the aperture and L represents the distancebetween the window and the target.

Further, by connecting a pipe 6 to a portion between window 7 and target5 in the chamber 1 and by introducing clean gas such as oxygen oralternatively, by evacuating through the pipe, the dust floating in thechamber can be removed, so that the effect of making clean the window 7can be enhanced.

In place of the aperture 4230a, a mesh grid 4230b such as shown in FIG.134c or an elongate grid such as shown in FIG. 134D may be used, toprovide similar effect.

FIG. 135 shows a modification of this embodiment in which a secondwindow 4231 is provided between window 7 and target 5. The second window4231 passes laser beam, and intercepts dusts scattered from the targetto prevent contamination of window 7. A thin window may be used aswindow 4231 since it is not necessary to keep chamber 1 airtight by thiswindow. Quartz, CaF₂, MgF₂ or a Teflon sheet may be used as the materialof the window. Further, by providing an aperture 4230 between the secondwindow 4231 and the target so as to limit the area of contamination ofthe second window and by making the second window movable, the laserbeam can pass through the clear area of the second window constantly.Though a second window is included in this example, a reflecting mirrormay be used. In that case, by changing the direction of progress oflaser beam 16 by using the reflection mirror, the dust emitted fromtarget 5 is prevented from directly reaching the window 7. However, evenin this case, the reflection mirror is contaminated gradually by thedust. Therefore, the surface of the reflection mirror which is exposedto the laser beam should be made changeable.

FIG. 136 shows a modification in which a nozzle 4232 is used in place ofthe aperture. Generally, in order to increase light intensity on thetarget, the laser beam is condensed. Therefore, when a nozzle 4232 isprovided along the condensed beam, the solid angle of the dust towardthe window can be limited and, in addition, the floating dust cannotreach the window 7. Therefore, deposition on window 7 can be reduced. Bysupplying clean material gas such as oxygen by connecting a pipe 6 to anozzle, the window 7 and the vicinity thereof can be kept clean and, inaddition, the material gas can be directly supplied to the periphery oftarget 5. FIG. 137 shows a modification in which a rotary chopper 4233is provided between the window 7 and the target 5. The chopper has aportion notched, and it is rotated along the arrow. The number ofrotation of the chopper and the frequency of laser generation areadjusted such that the laser beam reaches the target through the notchof the rotating chopper only during laser generation, with the laserbeam used for film formation being in the form of pulses. Since the dustscattered from the target are generated little later than the laserirradiation, the dust can be intercepted by the chopper before reachingthe window. Though a rotary chopper is shown in this example, any meanshaving the function of a shutter which is opened only during the passageof the laser beam can be used to provide the same effect.

FIG. 138 shows a modification employing a gate 4234. Though thedeposition on the window 7 can be reduced by various means, the windowmust be changed sooner or later. In that case, if the externalatmosphere is reached into the chamber 1, the inner side of the chamber1 is contaminated, degrading the function of the form film. Therefore,in this example, a gate 4234 is provided and a pipe 6 for evacuating orsupplying air to the window 7 and the gate 4234 are provided. After thegate is closed, the window is changed. Then, by repeating supply andevacuation of air by means of pipe 6, the vicinity of the window is madesufficiently clean, and then gate is opened again. By this series ofoperations, the window can be changed without exposing most part of thechamber 1 to the atmosphere.

FIG. 139 shows an embodiment in which the window 4235 is made largeenough with respect to the size of laser beam 16, and a mechanism forchanging the area of laser beam transmission of the window is provided.When a portion of the window 4235 is tarnished, the window is moved inparallel or rotated so that the laser beam passes through a clearsurface of the window. Consequently, the chamber can be usedcontinuously without exposure to the atmosphere until the window isentirely contaminated. Though a large window is used in this embodiment,a plurality of windows may be mounted on one window holder so that thewindow can be changed every time a window is tarnished.

FIG. 140 shows a modification including means for keeping clean theatmosphere side of window 7, different from other examples. Outer sideof the window is also gradually contaminated by the influence of dustfloating in the atmosphere or organic solvent. Therefore, there isprovided an optical transmission path between window and laser unit 10.Though dependent on the wavelength of the laser beam, the transmissionpath is filled with dry nitrogen, dry air or rare gas which do notabsorb laser beam. The inner walls of the transmission path are formedby a metal, which do not generate any gas even when it is irradiatedwith the scattered laser beam, for example, aluminum. If the laser beamis transmitted through such an optical transmission path, it does notattenuate on the way, and in addition, contamination of window 7 can besuppressed since the transmission path is kept clean. Condenser lens 9,a mirror for changing the direction of laser beam and so on may bearranged in the optical transmission path. Though the opticaltransmission path is filled with gas in this example, similar effect iseffected by keeping this path near vacuum.

Though various embodiments with respect to the window 7 have beendescribed, further effects can be obtained by combining these examples.

A ninetieth embodiment of the present invention will be described withreference to FIG. 141. In FIG. 141, the reference character θ representsan angle made by laser beam 16 and the normal of the surface of thetarget 5.

Referring to FIG. 141, in the present embodiment, the direction ofgeneration of the evaporated materials from the target when plume 15 isgenerated by laser beam irradiation of target 5 has cosine or similarspatial distribution. Therefore, largest amount of evaporated materialsare emitted to the direction of the normal of the surface of target 5.As the incident angle θ increases, scatter of the evaporated materialsin the direction of the incident laser beam becomes smaller. As a resultof experiment in which the incident angle θ is changed variously, it isfound that deposition of the evaporated materials on laser inlet window7 can be significantly reduced when the angle θ is set to 30°.Consequently, contamination of laser inlet window 7 can be significantlyreduced.

Ninety-first embodiment of the present invention will be described withreference to FIG. 142. The apparatus of the present embodiment includes,referring to FIG. 142, a laser 21 for monitoring, a detector 22, acontrol valve 23 of which opening/closing is controlled by a signal fromthe detector, and a barrier wall 24 for preventing disturbance of thefield by purge gas.

The operation is as follows. When a film is to be formed on a substrateby irradiating opposing target with the laser, laser 21 for monitoringis passed through inlet window 7 and its intensity is monitored bydetector 22. When reduction in light intensity caused by frost on thewindow is detected, the valve is opened by the control apparatus and thepurge gas is blown to the inlet window. Thus the frost on the window canbe removed. Therefore, film formation can be carried out with the laserintensity not attenuated by the frost on the window. Since there isbarrier wall 24, the purge gas do not disturb the field of filmformation.

As described above, by this embodiment, the intensity of the laser beamis not reduced by the frost on the window, and therefore a thin filmforming apparatus using laser allowing formation of a thin film havingsuperior film characteristics than in the prior art with uniform filmquality in the thickness direction can be provided.

A ninety-second of the present invention will be described withreference to FIGS. 143 and 144. The apparatus of this embodimentincludes, referring to FIG. 143, laser unit 10, lens 9 for condensinglaser beam from laser unit 10 to the surface of the target, a vacuumchamber 1, substrate 2, substrate holder 3, target 5, a lighttransmitting window 7, a mirror 374 and a driving apparatus 375.

The operation is as follows. The laser beam emitted from laser unit 10is condensed by the lens and focused on target 5 to provide necessarylight intensity. The laser beam passed through lens 9 is transmittedthrough mirror 374 and light transmitting window 7 of chamber 1 to beincident on target 5. Since the target 5 is irradiated with high densitylaser beam, a plasma is abruptly generated, and in the process ofcooling the plasma rapidly, isolated excited atoms and ions aregenerated. These excited atoms and ions have lives of severalmicroseconds, and generate a plume 15 which is like a flame. Meanwhile,substrate 2 is placed fixed on substrate holder 3 opposing to target 5.Excited atoms and ions in plume 15 reach the substrate 2 and aredeposited thereon, forming a thin film.

In this case, it is known that the thin film composition isapproximately the same as the target composition. In this embodiment,target 5 is divided into concentrical two portions as shown in FIG. 144,and the laser beam is directed bridging the two target compositionsshown in the figure. Therefore, a thin film having such a compositionwhich corresponds to the area of laser beam irradiation with respect tothe two compositions is formed on the substrate. When the composition ofthe thin film formed on the substrate is to be changed or adjusted,mirror driving apparatus 375 is driven to delicately adjust the opticalpath of the laser beam so as to change the area of laser beamirradiation of two target compositions. Thus the composition of the thinfilm can be easily changed.

A ninety-third embodiment of this invention will be described withreference to FIGS. 145 and 146. The apparatus of this embodimentincludes, in addition to the ninety-second embodiment shown in FIG. 143,a lens driving apparatus 376.

In this apparatus, referring to FIG. 145, the laser beam emitted fromlaser unit 10 is condensed by lens 9 and focused on target 5 to providenecessary light intensity. The laser beam which has passed through thelens 9 passes through mirror 372 and light transmitting window 7 ofchamber 1 to be incident on target 5. As the target 5 is irradiated withhigh density laser beam, a plasma is generated abruptly. In the processof cooling the plasma rapidly, isolated excited atoms and ions aregenerated. These excited atoms and ions have lives of severalmicroseconds, generating a plume 15 which is like a flame. A substrate 2is placed fixed on substrate holder 3, opposing to target 5. Excitedatoms and ions in plume 15 reach substrate 2 and are deposited thereon,forming a thin film.

In this case, it is known that the composition of the thin film isapproximately the same as that target composition. In this embodiment,target 5 is divided into concentrical three portions as shown in FIG.146, and the laser beam is directed bridging three target compositionsas shown in the figure. Therefore, a thin film having a compositionwhich corresponds to the area of laser beam irradiation corresponding tothe three components is formed on the substrate. If the composition ofthe thin film formed on the substrate is to be changed or adjusted,mirror driving apparatus 375 is driven to delicately adjust the opticalpath of the laser beam and the lens driving apparatus 376 is driven todelicately adjust the area of irradiation of the target with the laserbeam, so that the area of laser beam irradiation of three targetcomponents can be changed, and thus the composition of the thin film canbe easily changed.

A ninety-fourth embodiment of this invention will be described withreference to FIG. 147. FIG. 147 is a cross section of a raw materialtarget 580 and a banking plate 582 used in the thin film formingapparatus using laser in accordance with this embodiment. Raw materialtarget 580 is a sintered body provided by mixing oxide ceramic finepowder including barium oxide, strontium oxide, titanium oxide and soon, molding and compressing by hot press method and sintering thecompressed body at about 1000° C. On the surface of raw material target580, there is provided a depressed portion 581. At the time of hotpressing raw material target 580, a metal mold having a protrudingportion corresponding to the desired shape of the depressed portion 581is used, so that a desired depressed portion 581 is formed at the rawmaterial target.

The operation is as follows. When raw material target 580 is irradiatedwith laser beam 583, temperature of the surface of raw material target580 is increased rapidly, causing internal stress due to the differencein thermal expansion coefficients between raw material target 580 and abacking plate supporting the target. The depressed portion 581 providedat the surface of raw material target 580 prevents concentration of theinternal stress and prevents generation of cracks. In addition, sincethe shock at the time of pulse laser irradiation can be distributed,generation and development of cracks can be suppressed. In addition,since the surface area of the raw material target 580 is increased, theefficiency in absorbing laser energy can be improved.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A thin film forming apparatus using a laser,comprising:a chamber having evacuating means; a target placed in saidchamber; laser beam irradiating means for irradiating said target with alaser beam; and substrate holding means for holding a substrate on whicha material included in a plume generated from said target by laser beamirradiation is deposited; whereinsaid target includes a plurality oftargets each having an aperture through which laser beam is passed; saidapparatus further comprisingmeans for changing positions of saidplurality of targets, allowing irradiation of one said target with thelaser beam passed through said aperture of another said target.
 2. Thethin film forming apparatus using a laser according to claim 1,whereinsaid means for changing position of said target includes meansfor rotating said target.
 3. The thin film forming apparatus using alaser according to claim 1, whereineach said target and the substrateare arranged such that distance between a position of laser beamirradiation of said target and said substrate is equal for every saidtarget.